Four inmates allegedly involved in deadly clash between prison gang died of asphyxiation while being transferred to a safer lockup, authorities said Wednesday, as families of victims began to bury their relatives.

The Para state public security office said the four were discovered dead when the prison vehicle arrived in the town of Maraba.

They said vehicle had four compartments and was carrying 30 handcuffed inmates who were suspected of involvement in Monday’s clash gangs at the Altamira prison.

Authorities said the four who died were from the same gang and said they are investigating.

The prisoners were among 46 being sent to other prisons, including stricter federal ones.