Police officials said the clearance program, once widely criticized as slow to provide access to key information about emerging threats and terror investigations, has added needed intelligence to recent terror inquiries from Colorado to New York.

Boston Police Commissioner Ed Davis says some of the agency's officers with clearance authority assisted in the fast-moving May investigation into the unsuccessful bombing in New York's Times Square. Eight Boston officers have clearance, up from two or three in 2001.

"Prior to Sept. 11, this wouldn't have happened," Davis said. "Now, there is a feeling that we are right in the middle" of the war on terror.

Faisal Shahzad, arrested 53 hours and 20 minutes after the failed attack, pleaded guilty to the attempt in June.

Last year, New York police worked with their federal counterparts to thwart an attempted assault on the city's transit system by terror operatives with ties to Denver, New York Deputy Police Commissioner Paul Browne said.

The information shared can include intelligence about terror suspects as well as other criminal probes.

Part of the increase, federal and local officials say, is because of the rapid expansion of the terrorism task forces created after the 2001 assaults to disrupt future terror plots.

Since 2001, the number of terror units, which draw on federal, state and local investigators, have grown from 35 to 104 nationwide. The units are staffed with 4,433 officers and agents, up from 912 in 2001, FBI spokesman Bill Carter said.

Members of those units usually need a one-time clearance to view top secret information.

In New York, Browne said, there are 120 officers assigned to anti-terror units with the FBI, up from 17 before 9/11. He estimates about 200 officers are cleared to view classified information, including 80 who aren't detailed to terror units.

Clearance "becomes a necessary requirement" for work on classified cases, he said.

The clearance program, first widely offered to officers soon after the Sept. 11 attacks, was part of a shift in bureau strategy to improve a tense relationship with local police. At that time, police leaders, including members of the International Association of Chiefs of Police, complained the bureau wasn't sharing enough information about terror threats.

Despite the recent increase in clearance grants, FBI Assistant Director Ronald Ruecker, the bureau's liaison to local law enforcement agencies, said most officers still do not have access to classified information and "many don't need clearances."

Ruecker said the FBI is launching an effort to declassify information that can be shared with more local investigators.

"Trying to get everybody into the clearance arena is not the solution," Ruecker said, adding that clearances can be granted only after applicants — including chiefs — pass detailed background investigations. Those inquiries can take months to complete.

"There has been a paradigm shift from then (pre-Sept. 11) and now," Ruecker said. "The philosophy (among federal authorities) was protect what you can and share if you must. It isn't that way anymore."