Eighteen inmates were injured, three critically, during a prison yard fight Friday at a Maryland corrections facility in Baltimore, authorities said.

The fight broke out at the Metropolitan Transition Center about 1:30 p.m., corrections spokeswoman Major Priscilla Doggett said.

"... inmates were evaluated and determined they needed additional treatment for stab wounds," Doggett said. The inmates were taken to local hospitals, she said.

The institution is in process of being locked down.

Emergency crews found inmates at the institution about 2 p.m. with injuries ranging from lacerations to stab wounds, Baltimore Fire Chief Kevin Cartwright said.

"Our paramedics arrived here in quite a chaotic situation," Cartwright said. Paramedics had to wait briefly until correction officers were able to secure the yard before they could treat the injured, Cartwright said.

Prison officials said three inmates were rushed to local hospitals with serious injuries.

Details about the cause of the disturbance were not immediately available, but it involved several groups of inmates, some of whom were armed with homemade weapons Doggett said, and no corrections personnel were injured. The facility will remain on indefinite lockdown, and the emergency operations command center has been activated, which is normal operating procedure, she said. The entire facility, including cells, will be searched for contraband. All inmates were returned to their housing area by Friday afternoon.

Darryl Williams, president of AFSCME local 1427, which represents corrections officers at this and five other prisons in the area, said Friday afternoon, "What happened here today shows that prisons in Maryland are dangerous." He added that there is "an ongoing situation ... where inmates are having confrontations," according to correctional officers that he's talked to.

A spokesman for Gov. Martin O'Malley, Sasha Leonhardt, said the governor was "briefed on the event" but referred further questions to state corrections officials. Leonhardt did not say what O'Malley's reaction was or whether he planned to head to the scene.

"The governor was briefed on the event and continues to monitor it but for specifics I'm going to refer you to DPSCS."

The transition center, a minimum security facility, houses more than 1,700 inmates who have two years or less to serve on their sentences. It is located in part of the former Maryland Penitentiary, an imposing, gothic structure built in 1811 that was once a maximum security prison.