The director of the Bureau of Alcohol, Tobacco, Firearms and Explosives announced his resignation yesterday, six months after the launch of an internal investigation into questionable spending on a new headquarters and other items during his tenure.

Carl J. Truscott, a 22-year veteran of the Secret Service who took over as ATF chief in 2004, was under fire for his spending and management practices at a time when the agency was considering sharp cuts in the number of new cars, bulletproof vests and other basics it provides agents.

Officials declined to say yesterday whether the allegations played a role in Truscott's departure.

In announcing his resignation, effective Tuesday, Truscott struck a positive note, calling his time at ATF "fulfilling" and praising agency employees for their "professionalism and proficiency."

"While there is always more to achieve, of course, I am confident that we have laid the groundwork for ATF to continue to realize great progress," Truscott wrote. "Therefore, I have decided now is the time for me to pursue other challenges and opportunities."

A report on ATF is expected soon from Justice Department Inspector General Glenn A. Fine. His office has been investigating allegations that Truscott put through or proposed hundreds of thousands of dollars of unnecessary plan changes and upgrades to ATF's new 438,000-square-foot headquarters.

The building, under construction in Northeast Washington, is at least $19 million over budget.

Sources familiar with the project told The Washington Post earlier this year that Truscott planned to buy, among other things, nearly $300,000 in extras for the new director's suite, including a $65,000 conference table and more than $100,000 worth of hardwood floors, custom trim and other items.

These sources described Truscott as overly focused on the building's details, from soap dishes to tile colors, and said he wasted valuable time with innumerable project meetings and field trips to the site.

ATF has spent an additional $75 million for site acquisition, design, furniture and other costs, and officials are debating whether they can move into the building on time this year, sources have said.

Justice investigators have also questioned ATF employees about a costly trip that Truscott and others took to London last year and about allegations that ATF staff members helped assemble a school video report for a young relative of Truscott's, according to officials interviewed in the probe who declined to be identified for fear of retaliation.

Truscott has declined to comment on the allegations.

Attorney General Alberto R. Gonzales said in a statement last night that Truscott is a "leader in the area of law enforcement, with a long and distinguished career in government service."

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