A fire ripped through an overcrowded prison in Indonesia killing at least 41 inmates and injuring 73 more.

The blaze broke out just before 2am local time on Wednesday morning at block C of the Tangerang Penitentiary in Banten province. The wing, crammed with more than 120 prisoners, was being used to detain offenders with drug-related charges.

Corrections department spokesman Rika Aprianti said the fire had been extinguished but evacuations were still underway as of 9am.

At least 41 people, all inmates, were killed in the fire. Meanwhile, 73 others, including eight who suffered severe burns, were injured. They have been taken to two hospitals in Tangerang for medical treatment.

Investigators said they are looking at faulty electrical wiring as the source of the fire.

Police spokesman Yusri Yunus said: 'The initial suspicion is this was because of an electrical short circuit.'

The Tangerang Penitentiary, located on the outskirts of the Indonesian capital Jakarta, housed around 2,000 inmates — more than thrice its intended holding capacity — according to government records as of this month.