"They were collating prisoner data on remission, which was to be given on Independence Day, Aug 17," he said.

About 1,000 police and soldiers were deployed to guard the facility and undertake a massive hunt around the area on Friday to try and find prisoners still on the loose.

They included six people convicted of terrorism, Prakoso said. The prison had been holding a total of 11 terror convicts, he said.

Prisoners stand inside the burned Tanjung Gusta prison, which was set ablaze by inmates after a riot broke out, in Medan in North Sumatra province, July 12, 2013. [Photo/Agencies]

Some were jailed for their involvement in militant training at a camp in Aceh province where, police say, militants were planning Mumbai-style gun attacks on high-profile Indonesians.

The others were connected with a bank robbery to fund terror activities and the killings of police officers, police said.

Prakoso added that 55 escapees had so far been arrested after an all-night hunt in the area, including three convicted of terrorism.

A spokesman for the justice and human rights ministry, Goncang Raharjo, said that Tanjung Gusta was overcrowded.

"The prison capacity is only 1,054 but it now holds about 2,600 convicts and suspects on trials," he said. "Most prisons across the country have this problem."

Agence France-Presse