MEXICO CITY, July 6 -- At least 28 people were killed in a prison riot on Thursday between suspected members of rival gangs in a prison in southern Mexican state of Guerrero, according to local authorities.

The state government updated the death toll from original five to 28 as police searched the prison. Three other prisoners were lightly injured.

At a press conference, Guerrero's security spokesperson, Roberto Alvarez Heredia, said that the fight began around 4 a.m. in Las Cruces prison in Acapulco. The fighting took place within block 1, block 3 and in the yard.

No information has been given so far on the identity of the deceased but Heredia said the families would be notified first. He stated that the violence had been contained after the police took control of the prison and no detainees had escaped.

Heredia explained that "the incident began due to the permanent struggle of rival groups inside the prison."

Guerrero governor Hector Astudillo Flores has given an order to "get to the bottom of the events and to bring the full force of the law to bear on those responsible."

Heredia added that "the investigation will include all the public servants within the prison system."

This prison is the most crowded in Guerrero, with 2,100 prisoners, according to Mexican government statistics.