Updated

SAN JUAN, Puerto Rico (AP) — Dozens of homeless drug users have died inside a jail in western Puerto Rico in the last decade, the American Civil Liberties Union said in a report Thursday calling for an investigation into possible rights violations.

The ACLU said some of the 53 deaths between 2002 and 2008 at the Guerrero Correctional Institution potentially could have been prevented with better medical care.

"The alarming number of deaths at the Guerrero Jail and the failure to adequately investigate them may constitute deliberate indifference on the part of the jail's administration toward the medical needs of these prisoners," the report said.

All but one of those who died were in pretrial detention at the minimum-security prison, and 73 percent perished within their first week of confinement, according to the report. There were no signs of violence.

A spokeswoman for the U.S. Caribbean territory's corrections department, Sheila Padin Hernandez, said it was preparing a response to the report.

Officials said previously that many of the deaths resulted from the use of Xylazine, a horse sedative that addicts were injecting along with heroin.

William Ramirez, executive director of the ACLU in Puerto Rico, said victims in those cases likely could have been saved with quick medical attention. He said the precise cause of death remains a mystery in many cases because the government has not investigated properly.

"I suspect there is a lack of proper medical care while withdrawal is going on, but there might be other reasons. We really can't say," Ramirez said in an interview.

The ACLU launched its investigation in 2006 after hearing reports from the homeless community in northwestern Puerto Rico about police sweeping up addicts and taking them to detox at the jail in the west-coast city of Aguadilla.

Many were arrested for minor charges such as panhandling or vagrancy, according to the report. Some were detained for being under the influence of drugs.

"The average person would not be picked up and put in a prison like Guerrero for being out on the street," Ramirez said. "That only happens to people who are homeless."