The U.S. gave Nigeria four full-body scanners for its international airports in 2008 to detect explosives and drugs, but none were used on the man suspected trying to blow up a Detroit-bound flight, Nigerian officials say.

Umar Farouk Abdulmutallab, tracked by cameras through the security check, only went through a metal detector and had his bag X-rayed when he arrived at Nigeria's busiest airport to start his journey, the officials say.

The Soter RS scanners delivers 3-D images that would have shown something hidden under clothing. But a spokesman for the anti-drug agency, which operates the Nigerian machines, told The Associated Press that the one at Lagos airport is used sporadically and only on potential narcotics smugglers.

After clearing security at Murtala Muhammed International Airport, Abdulmutallab flew to Amsterdam, boarded Northwest Airlines Flight 253, and allegedly lit an explosive device hidden in his underpants as the plane approached Detroit on Christmas Day.

Even word of the scanners' presence in Nigeria's four main airports apparently hasn't reached top officials, including one responsible for airline safety.

Harold Demuren, the head of the Nigerian Civil Aviation Authority, told reporters Wednesday that his government would buy 3-D full-body scanners for the airports, and insisted there were currently none there.

But on Thursday, Ofoyeju Mitchell of Nigeria's National Drug Law Enforcement Agency, told the AP that one of the machines sits in a room near the security checkpoint in Lagos' often chaotic international airport.

He said they aren't used on every passenger. Instead, drug agents select frequent flyers, travelers heading to and from drug shipment points, and people who seem deceptive or under stress. Nigeria is a major transit point for Afghan heroin and South American cocaine.

"The frequency of checks is determined by the risk level of our assessment ... (and) reasonable cause for suspicion," Mitchell said.

Such limited use is not what the U.S. State Department intended when it gave Nigeria the scanners.

According to an April 30 U.S. State Department report, the scanners were installed in March, May and June of 2008 "to detect explosives and drugs on passengers."

The U.S. Embassy in Nigeria would not comment on the use of the scanners.

Reuben Abati, a columnist at Nigeria's Guardian newspaper, highlighted a different risk factor _ a culture of graft and favoritism that allows VIPs to bypass screening.