KABUL (Reuters) - U.S. authorities are looking into allegations that some Afghan Air Force (AAF) officials have been using aircraft to transport narcotics and illegal weapons across the country, a U.S. official said on Thursday.

"At this point allegations are being examined," said Lt. Col. Tim Stauffer, spokesman for the NATO Training Mission-Afghanistan, which is setting up and financing Afghan security forces, including the Air Force.

"Authorities are trying to determine whether the allegations warrant a full investigation."

The Wall Street Journal, which first reported the allegations, said the U.S. military is also looking into whether the alleged transporting of illegal drugs and weapons is connected to an April incident in which an AAF colonel killed eight U.S. Air Force officers at Kabul Airport.

A U.S. Air Force report about the deaths quoted American officials as saying that the killer was likely involved in moving illegal cargo, The Wall Street Journal reported.

Most of the victims had been taking part in an inquiry into the misuse of AAF aircraft, the newspaper said.

The allegations of drug running come from "credible" Afghan officers inside and outside the AAF and coalition personnel working within the AAF, it added.

The AAF was set up largely with U.S. funds.

The United States poured in a record amount, near $12 billion between October 2010 and September 2011, to train and equip Afghanistan's security forces. Almost as much cash, some $11 billion, is planned for the year through September 2012.

Afghanistan produces 90 percent of the world's opium and the drug trade is often blamed by Western officials for hindering economic development.

The poppy economy in Afghanistan, which provides an income for insurgents in the country blighted by decades of war, has grown significantly in 2011 with soaring prices and expanded cultivation, a U.N. report said late last year.

(Reporting by Michael Georgy; Editing by Sanjeev Miglani)