Investigators searched for clues on Tuesday on why a Ukrainian aircraft smashed into a Turkish mountain in thick fog, killing all 13 mainly Ukrainian crew and 62 Spanish peacekeepers returning from Afghanistan.

"Although we are known for being tough, we are devastated," said Spanish General Emilio Perez Alaman, whose mechanized division lost 20 soldiers when the Yak-42 charter plane crashed on Monday. There were no survivors.

As Turkish officials prepared to send home the bodies of the Spanish peacekeepers, investigators looked for the plane's black box flight recorder at the crash site near Turkey's northeastern town of Macka.

"The cause, according to initial indications, was the dense fog in the area," Spain's Defense Ministry said in a statement.

Charred bodies were strewn across a large area shrouded in mist and the plane was split in two pieces. The dead crew were 12 Ukrainians and a Belarussian.

One witness told Turkey's Anatolian news agency he saw the plane on fire in mid-air. "I saw a burning aeroplane. About two minutes later, I heard two explosions, then a few more explosions," villager Adil Yilmaz said.

Spanish Defense Minister Federico Trillo arrived in the nearby Black Sea city of Trabzon with a team of doctors and crash investigators to assist the Turkish investigation.

Turkish officials had removed the bodies from the wreckage and placed them in the local morgue.

The Spanish soldiers, nearly half the country's contribution to a peacekeeping force in Afghanistan, left the Kyrgyz capital of Bishkek on Sunday for Zaragoza, Spain.

Turkey's Transportation Ministry said contact had been lost with the plane when it was southwest of Trabzon's airport.

Volodymyr Gorbanovsky, deputy general director of the plane's owners, Mediterranean Airlines, said initial information indicated it had veered from its flight path because of fog.

The latest crash of a Ukrainian-owned plane adds to the growing list of malfunctions and tragedies casting a shadow over the country's air industry.

Earlier in May, the doors of a Ukrainian-owned Ilyushin Il-76 cargo plane burst open in mid-air, sending at least 14 passengers to their deaths in Congo.

Experts said lack of safety regulations and financing were to blame for Ukraine's grim record.

U.N. Secretary-General Kofi Annan, Pope John Paul and Afghanistan sent condolence messages.

"The troops were returning from having served...in the selfless contribution to the Afghan peace process," said a spokesman for Annan.