More than 100 inmates staged a violent uprising at the city jail in downtown St. Louis over the weekend, setting fires, smashing windows and throwing furniture and other objects to the sidewalk below, reports said.

A guard at the City Justice Center had to be treated at a nearby hospital but was not seriously injured.

No inmates were hurt after many picked the locks on the cell doors and freed themselves, according to Jimmie Edwards, the city’s director of public safety. Officials have been dealing with the problem since December, The St. Louis Post-Dispatch reported.

The rioters also managed to access a lock panel system and “other detainees were released from their cells into the unit,” Edwards said, according to NBC News.

On Monday, St. Louis Circuit Attorney Kim Gardner launched an investigation into the conditions at the lockup, where coronavirus pandemic restrictions have limited visits, stalled court proceedings and caused several other disturbances in recent weeks, officials said.

Saturday’s riot began about 2:30 a.m. when a “defiant” inmate allegedly attacked a corrections officer, authorities said.

Several other inmates in the fourth-floor unit also jumped in, reports said. Simultaneously, numerous other detainees who “jimmied” locks were free to roam the corridor. Although the situation was contained to one floor, inmates from a second unit converged in a hallway with the first group of rioters, and soon 117 inmates were involved in the mayhem.

Jacob Long, a spokesman for St. Louis Mayor Lyda Krewson, described the group as “extremely violent and noncompliant.” The inmates tossed a stationary bike, chairs and mattresses from the broken windows, and set small fires inside the jail. Some stood at the broken windows while chanting, burning linens and holding up crudely made signs as the mayhem played out on television and social media.

“There are some burn marks on the front of the building. They destroyed the inside of their floor and threw all sorts of stuff outside. ... They flooded the floors, clogged the toilets, clogged the drains, so there is water damage,” Long said.

Dozens of law enforcement officers worked for hours before bringing the insurrection under control shortly before 10 a.m., according to The Associated Press. Firefighters used a hose to put out the fires.

Long said 65 inmates have since been transferred from the downtown jail and into the St. Louis Medium Security Institution, also known as the workhouse. He also said law enforcement has talked to the prosecutor’s office and that those involved could face charges.

The riot was the third disturbance at the facility in recent weeks.

In late December and early January, dozens of inmates were transferred from the St. Louis City Justice Center after two separate disturbances. Officials have said inmates were upset about conditions in the jail amid the pandemic.

Although there were no confirmed cases of COVID-19 among the 633 people jailed at the St. Louis Justice Center as of Friday, tensions have been simmering.

“I imagine they are under the same amount of stress due to COVID restrictions like the rest of us are,” Long said. “Courts haven’t been hearing cases in the 22nd Judicial Circuit. Their family visits have been restricted. But also they are acting out and that is the current situation.”

On Sunday, advocates for inmates said the uprising was “an act of courage” that was necessitated by inmates’ basic needs not being met, including a lack of personal protective equipment to help stave off a coronavirus outbreak.

Gardner, in a statement, called the weekend incident and other recent protests inside the jail “deeply troubling” and said her office’s investigation will focus on the circumstances that led to the actions.

“We will ensure there is full accountability,” Gardner said. “But while some are calling for the immediate prosecution of the detainees involved, this situation demands further scrutiny.”

She cited concerns raised by relatives of detainees, public defenders and advocates about conditions, “including whether or not appropriate protocols have been followed to prevent the spread of COVID-19.”

Information provided by The Associated Press was used to compile this report.