A new state law that raised the age of criminal responsibility to 18 has caused a massive spike in violence at youth detention facilities, city officials admitted Tuesday at a City Council oversight hearing.

At one of the facilities, Crossroads Juvenile Center in Brooklyn, the use of physical restraints by staff jumped from 226 during the first quarter of the year to 396 in the last quarter ending in September. Fights between detained youth at Crossroads grew from 15 to 100 during that same time period, according to the Administration for Children’s Services.

The statistics were just as worrisome at the city’s second youth detention center, Horizon in the Bronx. Use of force incidents at Horizon nearly doubled from 99 in the first part of the year to 181 in the last reporting period.

There were 228 injuries resulting from the violence.

“ACS’ own data is very troubling,” said Councilman Rory Lancman (D-Queens) at the hearing on Raise the Age, which bars prosecutors from automatically charging 16- and 17-year-olds as adults. State lawmakers passed the sweeping criminal justice reform in April 2017.

The city moved all 16- and 17-year-olds at Rikers Island to Horizon in October 2018. Most of the city’s teens who are arrested are now put through Family Court instead of the adult criminal justice system.

Testimony submitted to the council from Legal Aid attorneys Nancy Ginsburg and Christine Bella said that the dangerous conditions at the juvenile detention centers mirror the atmosphere at the notorious Queens lockup.

“The city must move quickly to change conditions at Horizon before the culture of violence brought from Rikers Island becomes entrenched in this new facility,” they said.

The juvenile detention centers are currently run by the Department of Correction, but ACS has started to assume that responsibility.

“ACS is taking control and as that’s happening we’re seeing the numbers grow, which I think we can all agree, is in the wrong direction,” Councilman Keith Powers (D-Manhattan) said at the hearing.

DOC Assistant Commissioner Jean-Claude LeBec testified that some of the problems stem from making the centers have “less of an institutional feel.”

“Some of those things just weren’t appropriate for the group that moved in….school chairs that were not connected to the ground turned into weapons,” LeBec said.

He added that just 17 detainees with behavioral and mental health problems are driving the majority of the incidents.