WASHINGTON -- U.S. authorities have been taking samples from suspected terrorists captured in Afghanistan that could produce DNA profiles, but it remains unclear what use they will be able to make of the material.

Including an analysis of the samples in a federal DNA database apparently would require congressional approval because of existing limits on what can be placed in the database.

Until last year, that had been limited to DNA from someone convicted of a sex offense, from crime scenes and from missing persons cases. Congress expanded that in last year's anti-terrorism law to allow inclusion of DNA from anyone convicted of any violent crime as well as conviction on some terrorism-related offenses.

The New York Times reported in a story on its Web site prepared for Sunday print editions that the FBI is seeking permission to place in the database DNA from prisoners captured in Aghanistan.

FBI officials disclosed in January that they were collecting hairs that could yield DNA samples from prisoners as they were being processed in Kandahar, Afghanistan.

Some of the prisoners subsequently were sent to the U.S. Navy base at Guantanamo Bay, Cuba. Nearly 500 terror suspects are in U.S. custody, 300 at Guantanamo Bay and the rest at two locations in Afghanistan.

Thousands more are being held by Afghan forces and in Pakistan.

David Carle, spokesman for Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., said Saturday the panel's staff had not been informed of any FBI proposal to gather blood samples from the prisoners and include them in the database.

Blood is the most reliable method of obtaining DNA samples, although if a sample comes from a complete hair follicle it can be of the same quality as blood.

The FBI plan is being reviewed by the Justice Department, according to the Times.

Representatives for the FBI and the Justice Department did not return calls for comment Saturday by The Associated Press.

Officials believe adding genetic profiles of the terror suspects to the national database would he helpful in two ways, unidentified government sources told the Times.

U.S. interrogations of the detainees are shifting from focusing on extracting information that might prevent future terrorist attacks or locate al-Qaida members to trying to determine whom to prosecute and how.

As a result, those not tried by a military tribunal, in a U.S. civilian or military court or by their home countries could be released, Defense Secretary Donald H. Rumsfeld has said.