SAN JOSE — Security cameras installed earlier this week at the Main Jail by Santa Clara County Sheriff Laurie Smith received their first test Thursday when a fight involving up to 30 inmates erupted.

The melee was reported about 3:10 p.m. in the maximum-security housing pod of the facility at 150 W. Hedding St.

“That’s where we installed the cameras,” Smith said during a news conference. “We don’t have cameras in any of the other housing areas. They only went in last night. It’s interesting that it happened here.”

The jail was placed on lockdown as a result of the fight.

Footage released by the sheriff’s office shows the melee starting with two people and spreading to the rest of the pod. Smith said it wasn’t immediately clear what caused it or how many inmates were involved.

“But we’ve got video evidence, and we’ll be able to make those determinations,” Smith said.

The inmates appeared to use only their fists.

Smith said she did not know the full extent of the injuries to the inmates, but none were life-threatening.

The maximum-security housing pod holds about 60 inmates, half of whom were out of their cells for “recreational time” when the fight broke out, according to Sgt. James Jensen.

About 20 deputies broke up the melee using their hands and pepper spray, Smith said. No injuries were reported among them.

“They did a great job,” Smith said. “This is what we do every day in the jail. This will give you some indication of the tough conditions that our deputies work in and the good job that they do.”

Julio Alvarez, acting president of the Santa Clara County Correctional Peace Officers’ Association, said in a statement the cameras showed just how dangerous the county jails can be.

“Cameras are part of the solution,” he said. “We need to address the systemic problems that are making our jails unsafe for inmates and officers.”

After being told it would take two years and up to $20 million to install security cameras at the jails, Smith went to Costco and purchased a dozen of the devices for $761.24 on Wednesday.

The move came as three deputies appeared in court this week on charges of beating to death mentally ill inmate Michael Tyree in late August.

“It just shows how important cameras are,” said Smith, referring to the fight Thursday afternoon.

Asked whether she believed the incident would spur the county to install the devices more quickly, she said, “I think it was going to be accelerated anyway. This may step it up a little bit.”

Contact Jason Green at 408-920-5006. Follow him at Twitter.com/jgreendailynews.