A vast United States Government database, which serves as a repository for raw intelligence about terrorist suspects or their associates, has nearly doubled in the past five years to include 1.1 million people by the end of last year, according to data released by the National Counterterrorism Center.

The same database, known as the Terrorist Identities Datamart Environment (TIDE), contained about 560,000 names at the end of 2009, following the failed Christmas Day attempt to blow up a commercial airliner over Detroit.

The failed attack thrust the inner workings of the government database and watch-listing system into an uncomfortable spotlight when it was disclosed that the name of the Nigerian suspect — Umar Farouk Abdulmutallab — accused of trying to detonate an explosive wired into his underwear was included in the TIDE repository.

His name, however, was not elevated to a more exclusive list that restricts suspects’ access to commercial air travel.

Of the 1.1 million identities in the updated database, about 25,000 are U.S. citizens or legal permanent residents, according to the updated records. The list is said to feature some other Nigerians apart from Abdulmutallab.

The database is a product of the National Counterterrorism Center, which was established in 2004 as an arm of the U.S. intelligence network to better share information across government agencies.

Intelligence sharing was a key weakness highlighted by the 9/11 Commission in its review of government operations in advance of the 2001 terrorist attacks.

•Adapted from a USA Today report. Photo shows failed Nigerian bomber Umar Farouk Abdulmutallab, whose name is on the list.