ISTANBUL, Turkey (AP) – A quick-spreading fire burned down most of the cargo section of Istanbul’s Ataturk International Airport on Wednesday, forcing 2,000 workers to flee the thick black smoke that closed one runway to traffic and disrupted flights.

The inferno collapsed a large part of the cargo building, likely causing millions of dollars in damage.

Three people were treated for smoke inhalation, authorities said.

“Our biggest consolation is there is no loss of life,” said Mujdat Yucel, manager of the Havas cargo and ground services company.

Firefighting planes filled with water from the nearby Marmara Sea made more than 70 sorties to douse the flames, flying low and at an angle to avoid a nearby Turkish Airlines building. Dozens of fire trucks also responded, and the blaze was brought under control after more than four hours.

Authorities ruled out terrorism or sabotage and gave various possible causes for the fire, including a spark from a welder’s torch or a short-circuit.

“It was definitely not sabotage,” said Deputy Gov. Fikret Kasapoglu. “But there are various kinds of materials in there, flammable, explosive, so we have to be careful.”

However, a hard-line Kurdish group, the Kurdistan Freedom Falcons Organization, claimed responsibility for the fire, the Netherlands-based Firat News Agency reported. The Freedom Falcons are linked to the Kurdistan Workers Party, the main Kurdish guerrilla group.

Government officials refused to comment on the claim.

As authorities struggled to move parked cargo planes away from the burning building, thousands of passengers anxiously watched thick smoke rise from behind the large windows of the ultramodern terminal building, the main hub for domestic and international flights and which hosts millions of tourists each year.

The fire closed down one runway, causing delays of up to a few hours, but authorities said there was no security risk for flights and encouraged passengers to fly. Turkish Airlines planes could be seen landing even as the fire raged.

The fire, which began in a section where fuel depots were located, surrounded the building within minutes as workers fled in a panic.

“A huge black cloud came, it smelled like cables burning, the roof started burning,” cargo worker Omer Toplar said.

Toplar and hundreds of his co-workers watched from about 100 yards away and feared that the blaze could cost them their jobs.

Workers said the entire structure was in flames within five minutes.

“There was panic, no one thought the fire would get so big,” said Sebahattin Yildiz, who said he owned cargo that was lost in the fire.

The fire destroyed much of the cargo stored in the building, including textile products and gold shipments, officials said. They said they would need more time to estimate the damage, but that it would be considerable.

The body of a Malaysian citizen awaiting repatriation was also in the cargo area before the fire, airport official Vedat Mutfuoglu said, but it was unclear whether it burned in the blaze.

“We know that the body of a Malaysian citizen was brought here to be sent to his country, but because the area has not been investigated we can’t say anything definite,” Mutfuoglu said. He said inspectors could not enter the area because it remained too hot.

In addition, because the cargo section contained a wide variety of materials being exported and imported, there was still the danger for the fire to reach explosive materials, officials said.

Radical Islamic, leftist and Kurdish militants are active in Istanbul and Kurdish militants recently claimed responsibility for a major fire at an Istanbul factory.

Associated Press Writers Selcan Hacaoglu and Suzan Fraser in Ankara contributed to this report.