Pittsburgh Mayor Luke Ravenstahl's administration would not release documents yesterday that describe the appropriate uses of a Police Bureau GMC Yukon sport utility vehicle that he used for business and personal travel.

"The City of Pittsburgh cannot release them, they are 'Official Use Only: Sensitive Homeland Security Information,'" mayoral spokeswoman Alecia Sirk wrote in an e-mail response to questions.

In August, police Sgt. Mona Wallace expressed concern that Mr. Ravenstahl's use of the Yukon violated terms of the Department of Homeland Security and Pennsylvania Emergency Management Agency grant that paid for its purchase. She was threatened with a reprimand, which was then reduced to counseling, but that was nixed by Public Safety Director Michael Huss.

Her concern was that the vehicle "came from a grant, and it was only supposed to be used by her unit, but the mayor was using it," said Fraternal Order of Police attorney Bryan Campbell. "That could endanger the grant."

Sgt. Wallace is part of the Intelligence Squad.

The grant agreement that governs the Yukon's use is between the city and state, which passes funds from the Department of Homeland Security to local governments. The agreement was signed in March 2006 by then-director for intergovernmental affairs Dennis Regan, who is no longer with the city, and witnessed by Yarone Zober, who is now chief of staff.

According to the agreement, all equipment bought with the $59,942 grant "shall be used for only the purposes set forth" in two documents called the Buffer Zone Plans and the Vulnerability Reduction Purchase Plan.

The Pittsburgh Post-Gazette requested access only to portions of those documents that outline the "purposes set forth" for the Yukon, but the administration declined to provide any information from the plans.

The Department of Homeland Security's guidelines for Buffer Zone Protection Programs, under which the city's grant fell, indicate that the money is meant to support efforts to identify potential terrorism targets, determine vulnerabilities, develop security zones around them and implement protective and preventive measures. The guidelines also allow "other authorized equipment."

Mr. Ravenstahl used the Yukon as a substitute for the Chevy Impala in which his security detail normally transports him. He said he used it when the Impala was in the shop or he needed something larger, as when he traveled with a contingent to Harrisburg or to a Toby Keith concert at Post-Gazette Pavilion.

U.S. Attorney Mary Beth Buchanan has ordered a review of the "allegations regarding improprieties" by the mayor. Her office had no additional information yesterday.