PALAIOCHORI, Greece — Experts were poised to investigate the site of a plane crash in northern Greece Sunday to determine whether any dangerous chemicals or explosive cargo remains.

The An-12 cargo plane smashed into fields between two villages late Saturday. 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.

Serbian Defense Minister Nebojsa Stefanovic told a news conference Sunday that all eight crewmembers were killed. He said the plane was carrying 11.5 tons of Serbian-made mortar ammunition to Bangladesh, which was the buyer. It had taken off from the Serbian city of Nis and had been due to make a stopover in Amman, Jordan.

The plane was operated by Ukrainian cargo carrier Meridian, and the Ukrainian consul in Thessaloniki, who has arrived at the crash site, told local officials that the crew were all Ukrainian.

“These were illuminating mortar mines and training (mines). … This flight had all necessary permissions in accordance with international regulations,” Stefanovic said.

The plane crashed shortly before 11 p.m., about 40 kilometers (25 miles) west of Kavala International Airport. Minutes before, the pilot of the plane 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.

Drone footage shows that small fragments are all that is left from the plane. 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, not to leave their homes and to wear masks. Authorities said they did not know if there were dangerous chemicals on the plane, including those contained in batteries.

A special army unit that looks for nuclear, biological and chemical substances will comb the site, but is not expected to arrive before 1 p.m. (1000 GMT).

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

The mayor of the municipality of Paggaio, to which the two villages close to the crash belong, has banned vehicle movement on nearby roads.