At least 29 prisoners were killed and 19 police officers injured in clashes at a jail in western Venezuela on Friday, BBC reported.

The incident occurred in Acarigua jail when police special forces tried to stop a “massive” prison break-out. “There was an attempted escape and a fight broke out among [rival] gangs,” Oscar Valero, the public security secretary of Portuguesa state, told Reuters. “With police intervention to prevent the escape, well, there were 29 deaths.”

Valero also said the police officers had faced “a hail of gunfire” and that inmates apparently detonated two grenades.

While some prisoners rights groups blamed the inmates, other groups questioned the official version of events. Rights group Una Ventana a la Libertad said the clashes broke out when officers attempted to rescue visitors who had been taken hostage by the leader of the inmates on Thursday.

But Humberto Prado of the Venezuelan Prisons Observatory asked: “How is it that there was a confrontation between prisoners and police, but there are only dead prisoners? And if the prisoners had weapons, how did those weapons get in?” Prado said prisoners have been demanding government help to avoid being transferred to distant prisons where relatives cannot visit them.

He also claimed that authorities had entered the cell block to carry out searches and remove visiting women when the violence broke out, adding that the jail held 540 inmates though it was designed to hold only 250 people.

Venezuela has seen a number of violent prison showdown in recent years. In March 2018, 68 inmates died in a fire at a police jail.

In August 2017, at least 37 people were killed when a riot broke out in a prison in southern Venezuela.