"It was yesterday (Tuesday) morning about 4:00 am (0100 GMT). A C-17 shortly after departure from the airport had a flight emergency. They had an explosion in one of their engines," Captain Carrie Clear, of the 447 Air Expeditionary Group, told AFP.

One person was slightly hurt and the aircraft landed safely, she said.

The C-17, a cargo and troop transport plane, was carrying three crew and 13 passengers, Clear said.

"The cause of the explosion is still being investigated," she said.

A US defence official speaking on condition of anonymity in Washington said "they believe it was hit by a surface-to-air missile based on witness reports."

Carrie said that "of course" a missile strike is one possible cause but a bird strike or rock entering the engine also may have been responsible.

"They're looking at everything," Clear said.

In the only confirmed missile strike at the airport since major combat operations ended in Iraq on May 1, a DHL cargo plane was hit by a shoulder- fired SA-14 surface-to-air missile as it took off from Baghdad airport on November 22.

DHL resumed flights into Iraq on December 3.

WAR.WIRE