At least 37 prisoners have been killed during fighting between armed inmates and security forces at a prison in southern Venezuela.
Security forces raided the prison in Puerto Ayacucho the capital of the southern jungle state of Amazonas seeking to restore order.
Inmates had seized control of the facility several weeks ago.
Criminal gangs often effectively control prisons in the country, meaning inmates frequently have access to automatic weapons.
“This was a massacre,” tweeted the state governor Liborio Guarulla following the raid.
“At midnight special forces showed up and through the night we heard gunfire and explosions,” he said.
He added that the city’s morgue was overwhelmed and was struggling to handle so many bodies.
A city council member, Jose Mejias, said gunshots were heard all night.
“The government went in to try to regain control of the jail”, he said. “The prisoners resisted.”
The Venezuela state prosecutor’s office confirmed it is investigating 37 deaths in the region and that 14 officials had also been injured in the raid.
The death toll is the country’s worst since 61 people were killed in a prison riot in 2013.
Venezuela has around 30 prisons, many of which are overcrowded. But the facility in question only housed about 110 inmates, said Mr Guarulla.
The country’s prison system was built to hold about 16,000 inmates but around 50,000 people are estimated to be behind bars in the country, according to the Venezuelan Prisons Observatory.