Monterrey, Mexico: At least 13 people were killed when a fight broke out in a prison in the northern Mexican state of Nuevo Leon and security troops were sent in to quell the violence, a state security official said on Tuesday.

The battle inside the Cadereyta prison outside the city of Monterrey began overnight, officials said. Anxious family members gathered outside the prison during the day waiting for news of their loved ones.

A protest by inmates overnight had spiraled out of control, one prisoner was killed and a number of guards were taken hostage, Nuevo Leon state security spokesman Aldo Fasci told reporters.

Police were sent in to calm the disturbance but the fight soon escalated to involve around 250 inmates, he said.

‘Around five in the afternoon, the decision was made by security forces to use lethal force to prevent the murder of guards as well as stop the murder of inmates,’ Fasci said.

‘If we had not taken this decision, we would be talking about many more deaths,’ he said.

It was not immediately clear how many people were killed in the fight and how many were killed by security forces, he said. Eight more people seriously wounded, he said.

Rival gangs that are involved in drug trafficking, human smuggling, fuel theft, kidnapping and extortion have fueled bloody battles in Mexico’s overcrowded prisons.

At least nine were killed in a prison fight in the state of Tamaulipas on the U.S. border with Texas and at least 28 inmates were killed in July in a battle in a prison in the Pacific resort of Acapulco.