Experts were poised to search the site of an airplane crash in northern Greece early Sunday to determine what kind of cargo it carried.

The An-12 cargo plane, which took off from the city of Nis, Serbia, on Saturday, and was headed to Amman, Jordan, crashed shortly before 11 p.m. local time, about 40 kilometres (25 miles) west of Kavala International Airport. Minutes before, the pilot of the plane, which was operated by Ukrainian cargo carrier Meridian, had told air traffic controllers, that there was a problem with one of his engines and that he had to make an emergency landing. He was directed to Kavala airport but never made it there.

The plane is a Soviet-era four-engine turboprop cargo carrier.

Greek media reported there were eight people on the plane and that it was carrying 12 tons of “dangerous materials,” mostly explosives. But local officials said they had no specific information on the cargo and provided slightly varying numbers of people on board.

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Drone footage shows that small fragments are all that is left from the plane, which crashed in fields between two villages and dragged a small distance on the ground. Local residents reported seeing a fireball and hearing explosions for two hours after the crash. A plume of white smoke was still rising from the front end of the plane on Sunday morning.

Firefighters who rushed to the scene in the night were prevented from reaching the crash site by smoke and an intense smell which they feared might be toxic. Nearby residents were told to keep their windows shut all night, to not leave their homes and to wear masks. Authorities say they do not know if there were dangerous chemicals on the plane, including those contained in batteries.

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The teams of explosives experts which will soon operate onsite will be augmented by experts from Greece’s Atomic Energy Commission, authorities said.

The fire service has cordoned off the area at a radius of about 400 meters.

Nellas reported from Athens, Greece