Tangerang, Banten. At least 41 inmates still locked in their cells died after fire engulfed at the Tangerang Penitentiary in Banten, just south of Jakarta, early on Wednesday.

All but one victim are drug offense convicts, according to officials. The other dead inmate has been convicted of terrorism but identities of all the victims have yet to be revealed.

"According to data that I received, the death toll comprises 41 inmates, one is a terrorism convict  and the rest are drug offenders. Two of the dead are foreign citizens," Justice Minister Yasonna H Laoly said in Jakarta.

The incident also injured more than 70 others, with eight in serious condition.

"The penitentiary caught fire at around 1:45, it started from Block C2,” Jakarta Police Chief Insp. Gen. Fadil Imran told reporters at the scene.  

While investigation is underway, Fadil speculated that an electrical faulty could have sparked the deadly fire.

"The fire is presumably caused by an electrical faulty. It lasted for about two hours and is now put up by firemen, police officers and prison staff members,” he said.

Surviving inmates have been transferred to other blocks while the injured are being treated at two local hospitals, he said.

The prison is located on Jalan Veteran, Tangerang city, which is part of Greater Jakarta.

A Justice Ministry official said when the incident occurred, all cells were locked.

"During the fire, every cell was locked so some of the inmates couldn’t be rescued from their cells in time," said Agus Toyib, head of the ministry’s Banten office.

Correctional officials and the police are currently in the process of identifying all the victims, he said.

The prison houses 2,072 inmates and the burned Block C2 had 122 inmates, he added.