A senior defense official has acknowledged translators were hired for terrorist interrogations at Guantanamo Bay in Cuba with only limited security checks.

Charles Abell, the principal deputy undersecretary of defense for personnel and readiness, now admits the Pentagon rushed to fill a critical shortage of Arabic-language translators in the wake of the September 11 terrorist attacks on the United States two years ago.

Mr. Abell said that meant some linguists were hired with only limited background checks. He said that could account for the recent discovery of security violations by two translators who worked at the Guantanamo Bay detention facility for suspected al-Qaida terrorists and Taleban fighters.

"I think it's fair to say that folks who were brought on with sort of interim-level checks, and then the more detailed checks to follow, I think the results of that are as we are seeing here," said Mr. Abell at a Congressional hearing Tuesday. "We have found a couple who were not as trustworthy as we had hoped initially. But there was an initial push. I think we all recognized that we didn't have enough Arabic linguists already employed to meet those requirements."

There are some 70 translators working at Guantanamo, assisting in the interrogations of the estimated 660 detainees held at the U.S. Navy Base in Cuba.

Some of the translators are military personnel. Others are civilians.

One of the detained linguists is a senior airman named Ahmad al-Halabi, who has been charged with aiding the enemy and espionage, including passing classified material to Syria.

The other translator who has been arrested is a civilian named Ahmed Mehalba, who was discovered carrying classified information about Guantanamo during a routine customs check as he returned to the United States from a visit to Egypt.

In addition to the two translators, a Muslim military chaplain who worked with the Guantanamo detainees has also been charged with security violations.

As a result of the arrests, the Pentagon is conducting a security review at the base. The Federal Bureau of Investigation is working with the Defense Department to examine the way chaplains and translators are hired.