BISHKEK - Remains of two bodies have been found in the wreckage of a U.S. military plane that crashed in Kyrgyzstan, and authorities are still looking for a third person who was on board, officials said.

The refueling plane exploded in mid air when its cargo of fuel ignited on its way to Afghanistan on Friday, accident investigators said.

Experts were still trying to work out what led up to the crash, said Kuvan Mamakeev, the Kyrgyz state prosecutor responsible for investigating transport crimes and accidents.

"It could be because of the fuel, because of the engine, the weather conditions or the human factor," he told Reuters.

Remains of the two bodies were found on Saturday, and a third person on board was still unaccounted for, Kyrgyzstan's Minister of Emergency Situations, Kubatbek Boronov, added.

The Boeing KC-135 Stratotanker took off from the U.S. military transit centre at Kyrgyzstan's Manas airport, which U.S. forces maintain for operations in Afghanistan, with around 70 tonnes of fuel on board, a local ministry official said.

The wreckage of the plane was scattered over about a 3-mile area in a mountainous area near the Kyrgyz village of Chaldovar, the official added.

Related:

US military refueling plane crashes in Kyrgyzstan, Pentagon says

Officials: Seven died in US cargo plane crash in Afghanistan

A U.S. Air Force refueling plane crashed Friday in Central Asia, the military said. There was no immediate word on casualties.

The plane, a KC-135, crashed in northern Kyrgyzstan and was based at the U.S. military installation at Manas, near the Kyrgyz capital of Bishkek. Its mission is to refuel combat planes on patrols over Afghanistan.

The KC-135 usually has a crew of three.

Military officials were investigating eyewitness reports that the plane was on fire before it crashed. They were also looking into the possibility that the plane blew an engine or struck a bird.

“I was working with my father in the field, and I heard an explosion. When I looked up at the sky I saw the fire. When it was falling, the plane split into three pieces,” Sherikbek Turusbekov, who lives nearby, told The Associated Press.

On Monday, seven people were killed when an American civilian cargo plane, a Boeing 747, crashed shortly after taking off from Bagram Air Base in Afghanistan. It belonged to National Air Cargo, an upstate New York military contractor.

Six of those killed were from Michigan and the seventh from Kentucky, the company said. The Taliban claimed responsibility, but NATO quickly said that the claim was false and that there was no sign of insurgent activity at the time of the crash.

The United States leases the Kyrgyz installation for about $60 million a year. The contract is up in July 2014.

Reuters contributed to this report.

This story was originally published on Fri May 3, 2013 8:01 AM EDT