(In this August 1st story, adds dropped name of organization in third and fifth paragraphs)

NEW YORK (Reuters) - A rights group is seeking to determine if school and police officials in Long Island, New York, helped immigration authorities detain students illegally in the country on the basis of what it alleges are questionable allegations of ties to Central American gangs.

At least two students at Bellport High School in Suffolk County, a suburb of New York City, are being held in U.S. immigration detention facilities after being suspended from school.

They are among nine minors in Suffolk County that the New York Civil Liberties Union (NYCLU) said may have been detained by U.S. immigration agents because of unconfirmed ties to gangs.

The group filed Freedom of Information requests with the Suffolk County Police Department and the South Country Central School District on Tuesday, seeking any documents showing why the students were suspended and whether their identities were shared with federal immigration officers.

The NYCLU said students had been suspended for actions such as wearing a shirt with a basketball logo or displaying an El Salvadoran flag on a Facebook page. The group is trying to determine through its information request whether the suspensions triggered the ICE detentions.

Justin Meyers, assistant police commissioner in Suffolk County, said the department could not comment on organizations’ information requests but that police followed multiple protocols to ensure all gang identification measures were done accurately.

Meyers said police worked to build relationships with Hispanic communities so that people feel safe reporting crimes without being questioned about their immigration status. The department alerts federal immigration officials when someone who has committed a crime - or is positively identified as a gang member - is found to be in the country illegally, he added.

“If we have a violent gang member that we can’t build a case against, we will certainly work with Homeland Security Investigations to remove them from the streets,” he said.

School and U.S. Immigration and Customs Enforcement officials did not immediately comment.

U.S. President Donald Trump has pledged to combat the gangs and enforce U.S. immigration laws.

“Few communities have suffered worse at the hands of these MS-13 thugs than the people of Long Island,” Trump said in a speech on Friday in Suffolk County, where he referred to gang members as “animals.”

GANG KILLINGS

Growing crime attributed to gangs has raised concerns in Long Island, where there have been 17 killings tied to the MS-13 gang since January 2016, according to congressional testimony by Timothy Sini, commissioner of the Suffolk County Police Department.

Two Bellport High students were hacked to death in a Long Island park earlier this year in a suspected MS-13 attack.

U.S. immigration agents have been seeking to arrest teenagers who are suspected gang members who entered the country without guardians as part of widening enforcement operations, according to a memo seen by Reuters.

Lawyers and advocates said it was not often clear what authorities relied on to identify people with gang ties.

“There is no public criteria of what a kid has to be doing to be identified as an affiliate of MS-13,” said Bryan Johnson, a Long Island immigration attorney, who said he had seen an uptick since June in clients picked up by ICE who have no criminal history.

MS-13, also known as the Mara Salvatrucha gang, was founded like its rival, the Mara 18, in Los Angeles in the 1980s in neighborhoods populated with immigrants from El Salvador who had fled civil war. As deportees with criminal histories were sent back to their home countries, the gangs spread throughout Central America.

The U.S. Justice Department’s National Gang Intelligence Center estimates MS-13 has more than 30,000 members.