The state Department of Public Safety transferred 21 inmates reportedly involved in a riot at the Maui Community Correctional Facility to the Halawa Correctional Facility on Thursday morning.

Public Safety Director Nolan Espinda said in a press release that the inmates’ anger concerning overcrowding at MCCC led to the disturbances. MCCC’s total population of 410 is 109 inmates over the facility’s operational capacity, according to a department report on prison populations.

The Maui Police Department is conducting a criminal investigation into the riot. It’s not yet clear what penalties the 21 inmates might be facing.

They arrived on Oahu about 11:25 a.m. Thursday without any disturbances during the flight, according to the press release.

The 21 inmates are all pretrial detainees. Espinda said in a press release that the department is working with the courts to allow video conferencing between Maui and Oahu for their court proceedings. There’s no timeline yet for how long they might be on Oahu, department spokeswoman Toni Schwartz wrote in a follow-up email.

“Our priority was removing the people who instigated the unrest so MCCC staff could focus on returning operations to normal,” Schwartz said in an email.

The department is still questioning other inmates at MCCC to determine if any others were involved in the incident Monday, which damaged two modules. The department has not yet determined how much repairs may cost.

Two inmates were treated for minor injuries.

Hawaii’s overcrowded prisons have been a problem for years. About 1,458 Hawaii inmates are currently housed at the Saguaro Correctional Center in Arizona.

A total of 248 Halawa inmates were transferred to Arizona in 2017 for security upgrades in their modules. The work has not been completed.