Indonesian prison fire kills 41

A fire has killed 41 inmates in an overcrowded prison block in Indonesia's Banten province, a government minister says, injuring scores more in a blaze that police say may have been caused by an electrical fault.

The fire, the country's most deadly since 47 perished in a firework factory disaster in 2017, broke out at 1.45am local time on Wednesday in a Tangerang Prison block, said Indonesian law and human rights minister Yasonna Laoly, after visiting the scene.

"We're working together with relevant authorities to look into the causes of the fire and of course formulating prevention strategies so that severe catastrophes like this won't happen again," the minister said in a statement.

The minister said two of the dead were foreign nationals, one each from South Africa and Portugal, and confirmed the prison was operating in overcapacity when the fire broke out.

Cells were locked at the time, the minister said, but with the fire raging uncontrollably, "some rooms couldn't be opened."

Earlier on Wednesday, Rika Aprianti, a spokeswoman for the ministry's prison department, said 122 were being detained on drug-related offences in a block built to hold 38.

Rika said all 41 fatalities were inmates, adding authorities were still evacuating the facility as of 9am local time.

Prisons in Indonesia are notoriously overcrowded, with experts saying the phenomenon is partly due to the emphasis on incarceration rather than rehabilitation of those convicted of drug-related offences under the country's strict narcotics laws.

On Wednesday morning local TV showed footage of flames engulfing the detention facility, and later, the building's charred remains as victims were pulled from the scene in orange body bags.

Dr. Hilwani from Tangerang General Hospital told Reuters that some of the bodies had been so badly burned they were unidentifiable.

Metro TV cited a police report saying that 73 people also had suffered light injuries.

"The initial suspicion is this was because of an electrical short circuit," police spokesman Yusri Yunus told the broadcaster.

The electrical wiring at the prison had not been upgraded since 1972 when the prison was built, minister Yasonna told Wednesday's briefing.

The prison in Tangerang, an industrial and manufacturing hub on the outskirts of Jakarta, housed more than 2000 inmates in total, far exceeding its 600 capacity, according to government data as of September.

Leopold Sudaryono, a criminologist and PhD candidate at the Australian National University, said that overcrowding also complicated emergency evacuation efforts.

"At the Tangerang prison there are only five guards working one shift to guard a prison with 2079 people" he said. "So fire detection efforts and evacuations are difficult."

Prison department spokeswoman Rika told local media that 13 guards had been on duty at the facility at the time of the blaze.