The death toll from a devastating prison fire in Indonesia has risen to 44, authorities said Thursday, as families rushed to submit DNA samples to identify inmates' remains.

The toll had stood at 41 a day earlier, after the blaze tore through the overcrowded prison in Tangerang, just outside the capital Jakarta, during Wednesday's early hours.

But justice minister Yasonna Laoly said three of the eight seriously injured prisoners died in hospital Thursday.

"Their remains are still at the morgue, we are coordinating with the families for them to be able to pick the bodies up" for burial, Laoly told reporters.

The bodies did not require DNA testing because they were still identifiable, despite suffering up to 90 percent burns, the minister said.

Police had received 31 DNA samples from the families of some of those killed, to help with identification.

Authorities were still investigating what caused the fire, which spread quickly through the penitentiary while most of the prisoners were asleep, locked in their cells.

At about 3 am (2000 GMT Tuesday), firefighters extinguished the blaze, which was mostly contained within one block housing prisoners jailed on drug charges.

Among possible causes suspected was an electrical fault.

Authorities said the prison's electrical system had not been upgraded since it was built in 1972, but the massive death toll has mainly been blamed on overcrowding.

The jail had just over 2,000 inmates, according to a government website, more than three times its intended capacity.

The block where the fire broke out had a maximum capacity of 40 prisoners, but housed 120.

Overcrowded, unsanitary conditions are common in Indonesian prisons, which contain about 270,000 inmates, and jailbreaks are frequent.