In Barrio Obrero, a predominantly Dominican neighborhood in Puerto Rico, the chilling effect of unprecedented immigration raids in the U.S. territory has been paralyzing. With homes and businesses desolate, a truck with speakers has been cruising through the streets of the working-class neighborhood with a message. "Suddenly, in that darkness, they heard: 'Immigrants, you have rights,'" Ariadna Godreau, a human rights lawyer in Puerto Rico, told NBC News. The legal nonprofit she leads,Ayuda Legal Puerto Rico,hired the truck, known as a "tumba coco," to make people aware of their rights and announce the launch ofa new hotline, the first in Puerto Rico providing legal support to immigrants, Godreau said. Over 300 families have already called the hotline and spoken with attorneys free of charge as they figure out their legal options in the face of a changing immigration landscape, Godreau said. Residents in Puerto Rico now fear that President Donald Trump's efforts to carry outmass deportationswill fundamentally change how immigration policies are enforced in a U.S. territory that hadlong been perceived as a sanctuary for immigrants. That perception was first shattered on Jan. 27, the same week Trump took office.Immigration authorities raidedBarrio Obrero andarrested more than 40 people.Witnesses toldTelemundo Puerto Rico, NBC's sister station on the island, that they saw agents break down the doors of several homes and businesses. Detainees were handcuffed, placed in vans and taken away, they said. In his 40 years living in Puerto Rico, Ramón Muñoz, a Dominican immigrant, had seen authorities sporadically detain undocumented people but never "with the aggressiveness" displayed during that raid. Complicating matters for immigrants in Puerto Rico, those detained are transferred to the mainland U.S. — an ocean away from their families and attorneys managing their immigration cases — becausethere are no permanent detention centerson the island that can hold detainees for prolonged periods, according to Rebecca González-Ramos, the special agent in charge of Homeland Security Investigations in San Juan. Aracely Terrero, one of the atleast 732 immigrants arrested by federal immigration authorities in Puerto Ricoso far this year, spent a month being bounced around three different detention centers in the States before she was released last week after animmigration judge determined she should have never been detained in the first place. A local police officer in the coastal town of Cabo Rojo alerted federal immigration authorities about Terrero after the officer found her selling ice cream at the beach without business permits, Telemundo Puerto Rico reported. Terrero hada visaand was in the process of obtaining a green card when she was taken into immigration custody, her attorney Ángel Robles and Annette Martínez, the executive director of the American Civil Liberties Union in Puerto Rico, told NBC News. Local policies in Puerto Rico limit coordination between local law enforcement and federal immigration authorities, Martínez said. Yet the ACLU in Puerto Rico is seeingmore cases in which local policeare suspected of racially profiling Dominican immigrants with the purposes of alerting federal immigration authorities, reigniting concerns about the revival of "discriminatory policing practices" that led topolice reforms in Puerto Rico a decade ago, Martínez said. Terrero's case also spotlighted how difficult it is for families and attorneys to keep track of detainees once they are sent to the States, Martínez added. "It was a nightmare,"Terrero told Telemundo Puerto Ricofollowing her release. "It was a very difficult journey because I'd never been arrested in my life. I'd never seen myself like this, with handcuffs, like a criminal." González-Ramos, the HSI special agent, said ina local radio interviewlast week that her office had been preparing to ramp up immigration enforcement efforts in Puerto Rico since November. She said they started "reorganizing" resources and "shifting priorities" after Trump's win. Yet the big raid on Jan. 27 came as a surprise to most people. Puerto Rico Gov. Jenniffer González-Colón had reassured immigrants in an interview with Telemundo Puerto Rico that same week that Trump was only "focused on what's happening in Mexico and in the United States, on that border." It helped create a "false sense of security," Godreau said. "These consecutive raids then begin in areas historically inhabited by the Dominican population." As immigration authorities escalate their efforts in Puerto Rico byraiding hotels, construction sitesand neighborhoods,more than 500 of the immigrants arrested so farare from the Dominican Republic. Dominicans make up the biggest share of Puerto Rico's immigrant population. Over100,000 Dominicans are estimatedto live in Puerto Rico. About a third are thought to be undocumented. Many of them are business owners or work hospitality, construction andelder care jobs,the last two being industries grappling with labor shortages, Godreau and Martínez said. González-Ramos had said her office would be detaining people illegally present in Puerto Rico, "specifically those whose criminal records pose a threat to our communities and national security." But only 13% of the 732 immigrants arrested this year have a criminal record,according to datafrom Homeland Security Investigations in San Juan. Following a subpoena from Immigration and Customs Enforcement, the administration of González-Colón,a Republican who supports Trump,recently handed over the names and addresses of 6,000 people who got driver's licenses under an immigrant-friendly law from 2013 that allowed people without legal immigration status to get them. González-Colón has said shewon't challenge Trump's immigration policiesso as not to risk losing federal funding. "The governor's attitudes and expressions have been quite misleading," Martínez said, adding that local jurisdictions frequently challenge and oppose federal policies in an effort to protect local residents. A spokesperson for Homeland Security Investigations in San Juan told NBC News that González-Ramos was not available for an interview this week. But inher local radio interviewlast week, González-Ramos said immigration agents periodically carry out "daily interventions" in an effort to find over 1,200 people who have final deportation orders "that we must execute." Everyone arrested in raids, regardless of whether they have final orders of deportation or not, "must be detained, no matter what," González-Ramos said in Spanish. "Right now, those are the instructions." The ACLU's Martínez said that in Puerto Rico, immigration arrests have an "aggravating factor": Those immigrants arrested are put on a plane and sent away to detention centers in the mainland U.S. For more than a decade, the island has lacked a working immigration detention center that can permanently house detainees. As immigration arrests ramp up, "temporary detention centers" have sprouted across Puerto Rico, according to González-Ramos. One of them is in a federalGeneral Services Administration buildingin Guaynabo.Equipped with almost 20 beds, it's been nicknamed "la neverita," or the icebox, by immigrants who have spent time there before being transferred to the U.S. An old ICE facility in Aguadilla thatshuttered in 2012was recently reopened to temporarily hold detainees, according to Godreau and Martínez, who have heard from immigrants taken there. Before its closure over a decade ago, "complaints were made at the time about the inhumane and inadequate conditions in which detainees in that center were held," Martínez said in Spanish. Mayor Julio Roldánapproved an ordinance Thursdayto declareAguadilla a "sanctuary city" for immigrantsin response to escalated enforcement efforts in the area. When at least two dozen detainees are at the temporary holding facilities, ICE planes come to Puerto Rico to transport them to permanent detention centers in different states,according to González-Ramos. Many of them are placed in immigration detention centers in Florida and Texas. But detainees from Puerto Rico have also been found in facilities in Louisiana and New Mexico. "We're seeing a pattern of disappearances," Martínez said, pointing out that in Terrero's case, it took the ACLU and her attorney weeks to find out where she was being held. The situation raises concerns over "multiple violations of human rights and civil rights," Martínez said, adding that the ACLU is continuing to monitor these cases and call for changes in local policies to ensure immigrants' rights are protected.