BISHKEK, May 3 (Reuters) - A U.S. airman who shot and killed an airport fuel truck driver at an airbase in the Central Asian state of Kyrgyzstan last year was flown home in March but remained under investigation, the U.S. embassy said on Thursday.

Kyrgyz officials had demanded that the airman, identified by the Foreign Ministry as Zachary Hatfield, be handed over for trial after the fatal shooting of Alexander Ivanov, 42, in December.

"The airman departed Kyrgyzstan on March 21," a U.S. embassy spokesman said in an email statement. "The U.S. investigation into the shooting continues and we continue to collaborate closely with Kyrgyz authorities about it."

The 376th Air Expeditionary Wing, which has about 1,000 troops based at the country's main Manas civilian airport, said at the time of the shooting that Ivanov threatened the airman with a knife during questioning at a checkpoint.

U.S. officials have not confirmed the airman's identity.

The military said the driver was shot twice in the chest in accordance with standard procedure when the Air Force's security force members feel their life is threatened.

Colleagues and relatives of Ivanov say they do not believe he was a threat and that the knife found at the scene was standard maintenance kit allowed in drivers' cabs under Air Force regulations at Manas.

Reflecting public anger over the shooting, Kyrgyzstan's government briefly threatened in December to evict all U.S. troops from the base, which is used to support operations in Afghanistan.

The U.S. embassy said the airman only left Kyrgyzstan after a Kyrgyz investigation was completed on March 9. The airman's home base commander would decide how to proceed after the U.S. investigation ended, it said.

An official from Kyrgyzstan's General Prosecutor's Office, Sumar Nasiza, said: "The Americans declined to hand him over because he is under U.S. jurisdiction... They have said they will complete their investigation and pass the material over to a U.S. military court."

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