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A Chicago Bulls jersey. A Facebook post of a Central American country’s flag. Playing soccer with classmates.

These are things that led to nearly a dozen high school students being falsely labeled as gang members and sent to immigration detention facilities far away from their Long Island homes, the New York Civil Liberties Union said.

The NYCLU said at least nine high schoolers from Suffolk County have been placed in “high security” detention facilities after being identified as potential members of MS-13.

“No child deserves to have his life upended or be ripped away from family based on flimsy allegations,” NYCLU Executive Director Donna Lieberman said in a statement. “Children who in many cases came to America to flee gang violence are being disappeared to face deportation without adequate protections or investigation.”

Christopher Dunn, an associate legal director for the NYCLU, said that the organization has learned, through talking with the students’ families, that school officials alerted police when they believed to have identified gang members. In turn, police officials contacted federal immigration authorities, and the students were detained.

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Dunn said he’s concerned that students “engaging in innocent behavior” could be wrongly identified by school officials, leading to the uprooting of these students’ lives.

“If kids are detained, we’re pushing very hard for immigration authorities to sort out as quickly as possible any allegations that are gang-involved and to release kids who aren’t,” Dunn told Fox News. “Our real concern from the outset is that there has not been a serious process to ensure that only gang-involved kids are being picked up.”

The organization wrote Thursday to the U.S. Office of Refugee Resettlement, which has jurisdiction over minors who enter the U.S. illegally unaccompanied by their parents, saying it believed the teens' detentions violated a federal court order and U.S. law.

MS-13 violence on Long Island began to get attention last summer, when two students at Brentwood High School — Nisa Mickens, 15, and Kayla Cuevas, 16 — were beaten and hacked to death in a suspected gang attack. They were among 17 people believed to have been killed by the gang on eastern Long Island since the start of 2016. Most of the people arrested in those killings were in the U.S. illegally, law enforcement officials have said.

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"No child deserves to have his life upended or be ripped away from family based on flimsy allegations."

Immigration and civil rights lawyers, though, said a crackdown in some Suffolk County schools has gone too far.

The NYCLU said one student was suspended for wearing a Chicago Bulls shirt, a possible gang symbol, to school and another for posting an El Salvadoran flag on a Facebook page.

Dunn said he’s been told that schools admit to not giving advanced warning on what clothing they believe to be evidence that a student is involved with a gang.

“That creates this situation with kids where you go to school and have no reason to think there’s going to be a problem, but all of a sudden you’re labeled as a MS-13 gang member,” he said.

He encouraged school authorities and federal officials to be “very, very careful” when determining if someone is involved with a gang.

“We think that that has not happened. They’ve been much too fast to pick up kids on unfounded allegations based on clumsy things like a basketball jersey that they might be wearing or something they posted on the internet which falls far short of the sort of evidence you want to see before somebody labels you a gang member,” Dunn said.

The NYCLU believes that the students are still detained, he said.

The Associated Press contributed to this report.