BOSTON (AP) — Newly released documents show Boston’s public school system has been cooperating with federal immigration authorities more extensively than officials previously suggested.

The school district made at least 135 student incident reports accessible to U.S. Immigration and Customs Enforcement officials, most of them between 2014 and 2017, according to documents released Monday by Lawyers for Civil Rights.

The organization is among a number of groups suing the city to release records about its ties to ICE, despite Boston’s sanctuary city policy.

“The extent of BPS collusion with federal immigration enforcement is alarming, and much more extensive than the city has let on,” said Janelle Dempsey, an attorney with Lawyers for Civil Rights.

The school reports were made available to ICE officials via the Boston Regional Intelligence Center, or BRIC, a law enforcement information hub run by the Boston Police Department with federal funding, according to the documents. School officials previously suggested they were aware of only one such instance of information sharing.

Lawyers for Civil Rights said the district needs to cease the cooperation because it is creating a “school-to-deportation pipeline.”

The organization sued the city after a request for public records about the district’s relationship with ICE was denied.

The records request was prompted by the deportation of a high school student to El Salvador in 2017. Immigration officials cited, among other things, a school incident report that alleged the student was an associate of the gang MS-13.

School officials stressed in a statement to The Associated Press that they do not share confidential student information with ICE. The police department said in a separate statement that there are strict controls on how ICE officials can access information on the regional intelligence center.

But school officials also acknowledged that incident reports generated by police officers posted in the schools aren’t considered protected student records and may be shared within the police department if they involve criminal investigations or are relevant to public safety matters.

The district said it updated its policy in 2018 to reflect stricter guidelines on how school police officers share their incident reports with other law enforcement agencies, including ICE.

Democratic Mayor Marty Walsh also defended the process Monday, noting that immigration status is not included in school incident reports, and that only serious threats are sent to the intelligence center.

Walsh signed into law last month amendments to the city’s Trust Act that place clearer limits on police in their cooperation with ICE.

(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)