Reuters/Jakarta

All 54 people on board a Trigana Air aircraft were killed in a crash two days ago in Indonesia's Papua province, the latest in a string of aviation disasters in the Southeast Asian archipelago, officials said on Tuesday.

Major-General Heronimus Guru, operations director at Indonesia's National Search and Rescue Agency, told a news conference in the capital that the passengers' remains were being put into body bags and recovered.

Officials have declined to comment on the cause of Sunday's crash until the results of an investigation by the national transport safety committee, but Guru said the terrain in Indonesia's easternmost province may have been a factor.

"There's a possibility the aircraft hit a peak and then fell into a ravine because the place that it was found is steep," he said.

Treacherous terrain of forest-covered ridges hampered rescuers' efforts to reach the site where the Trigana Air Service ATR 42-300 plane came down.

The aircraft's black box flight recorder, which should provide investigators with some answers, was found in the early afternoon, Transport Ministry spokesman Julius Arivada Barata told Reuters by text message.

There were 44 adult passengers, five children and infants and five crew on the short-haul flight from provincial capital Jayapura  south to Oksibil town.

The twin turboprop aircraft was also carrying about $470,000  as part of a village assistance programme.

Poor infrastructure in the province means aid money is often flown in by air, said Abu Sofjan, spokesman for the national postal service, four of whose workers were among the passengers.

There was no suggestion the money was somehow linked to the crash.

Five members of the Bintang Highlands district parliament and government were also on board, online news service detik.com reported. Reuters was not able to verify the report.

All on board were Indonesian, officials have said.

Officials of Trigana, placed on a European Union list of banned carriers since 2007 over safety or regulatory concerns, were not immediately available to respond to questions from Reuters.

The aircraft made its first flight 27 years ago, the Aviation Safety Network says. Trigana Air Service has a fleet of 14 aircraft, aged 26.6 years on average, according to the airfleets.net database.

Trigana has had 14 serious incidents since it began operations in 1991, online database Aviation Safety Network says. Besides the latest crash, it has written off 10 aircraft.

Indonesia has a patchy aviation record, with other two major crashes in the past year.

In December, an AirAsia flight went down in the Java Sea, killing all 162 aboard. More than 100 people died in June in a crash of a military transport plane.

Indonesia scored poorly on a 2014 safety audit by the U.N. aviation agency largely because its Ministry of Transportation is understaffed, said two sources familiar with the matter, as the country struggles to cope with the rapid expansion of air travel.