A police official contacted by AFP was unable to provide further details.
Most detainees at the prison have been convicted of common crimes or were supporters of former dictator Moamer Kadhafi, found guilty of killings during the uprising that toppled his regime in 2011
According to a health ministry toll, at least 39 people have been killed and some 100 injured since clashes, including rocket fire, broke out among rival militias Monday in suburbs south of Tripoli.
Rocket strike on camp
And on Sunday rockets hit a camp for displaced people in Tripoli, leaving at least two dead and five injured from the same family, according to emergency services and witnesses.
The camp is home to hundreds of displaced people from the Libyan city of Taourga who were forced into mass exile due to their support for Kadhafi.
"Most of the families have left the camp fearing more rockets," Khaled Omrane, a camp resident, told AFP.
According to emergency services, at least 23 rockets fell on the capital on Friday and Saturday causing fresh casualties.
Refugees inside the camp have told reporters guards assigned to watch over them had fled during the attack, taking provisions left by international aid organisations.
The Government of National Unity (GNA) which is recognised by the international community on Sunday said it was declaring a state of emergency in the Libyan capital and its environs.
The Libyan capital has been at the centre of a battle for influence between armed groups since Kadhafi's fall and killing.