A riot erupted early Friday at a federal prison in Texas. One inmate was killed and 22 other were injured, officials said.

The Federal Correctional Institution in Three Rivers, which houses 1,160 men, was put under lockdown the Federal Bureau of Investigation is carrying out an inquiry according to the Bureau of Prisons.

The fights broke out at approximately 6:20 a.m. when two fights between separate gang members broke out almost simultaneously. The riot was eventually suppressed with the help of some of the prison’s staff members including plumbers, electricians and secretaries.

Police identified the dead inmate as Servando Rodríguez, a 38-year-old illegal immigrant. He had been convicted for marijuana and parole violations. He was stabbed to death, police said.

Fifteen other inmates were rushed to the nearest hospitals. Two of them were listed in critical condition, three returned from the hospital after being treated and seven were treated of their injuries at the prison’s medical facility.

Fortunately, no prison employees were harmed in the riot.

The union leaders released a statement in which they tried to explain the reasons for the latest increase in violence in prisons across the state of Texas. The main reasons are understaffing and the increasingly violent inmates.

This is the second prison riot that occurred this month. A similar quarrel erupted at the Federal Detention Center in Houston on March 11. Over 80 prisoners were involved in the fight; 9 inmates and 3 employees were injured.

Investigators are currently trying to find out whether the fights that broke out at Three Rivers came as retaliation between Pisa, a Californian gang, and another called the Mexican Mafia.