A fire at a police station in the city of Valencia, in Carabobo state, Venezuela has left 68 people dead, government officials say.
The blaze reportedly started after prisoners set fire to mattresses in an attempt to break out on Wednesday.
Police used tear gas to disperse relatives who surrounded the station after news of the fire broke.
Chief state prosecutor Tarek Saab said an investigation into what had happened would begin immediately.
State official Jesus Santander said the situation had now been been brought under control. He said the state of Carabobo was in mourning.
The circumstances surrounding the fire have not been officially confirmed.
The association Una Ventana a la Libertad (A Window on Freedom), which monitors jail conditions, said its reports showed a police officer had been shot in the leg by a detainee and that shortly afterwards mattresses in cells were set ablaze and the fire quickly spread.
Mr Santander did confirm one police officer had been shot.
Rescuers reportedly broke through walls to try to free those trapped by the blaze.
Nearly all of those who died were inmates but at least two women who were visiting at the time were also killed, Mr Saab said.
Some of the victims burned to death, others died of smoke asphyxiation.
Angry relatives gathered outside the detention centre clashed with police as they sought information about loved ones.
Aida Parra, who said she had last seen her son the day before, told the Associated Press news agency: "I don't know if my son is dead or alive. They haven't told me anything."
Dora Blanco told local media: "I am a desperate mother. My son has been here a week. They have not given any information."
The Venezuela government has set up an inquiry.
Carabobo state governor Rafael Lacava expressed his condolences, adding: "A serious and profound investigation has been initiated to find the causes and those responsible for these regrettable events."
Inmates are supposed to be held for only 48 hours in police holding cells.
Carlos Nieto, head of Una Ventana a la Libertad, says some police facilities are overfilled at five times their capacity.
The organisation says that 65 people died last year in temporary cells due to violence, disease or malnutrition.
Last month inmates at a different prison in Carabobo took a number of prisoners and guards hostage in another riot.