Prince William County and state investigators are probing allegations that county building inspectors falsified records and received bribes to approve faulty or incomplete construction work at new housing sites.

The three-week-old investigation is focusing on alleged inspection irregularities to the Northern Virginia county, where a building boom has been accompanied by an extraordinary number of homeowner complaints about shoddy construction and broken promises by developers.

County police say their investigation is concentrating on a subdivision in the southeast portion of the county owned and developed by Tray-Marc Construction Co. Inc. of Dumfries. Investigators say county records reveal that at least one building inspector approved work that was never done at the subdivision.

"Something stinks in the building records. Whether it's willful falsification or not it's hard to say. That's what we're investigating," said Prince William County Investigator David Lagerveld.

The inspector, who has not been identified, was put on administrative leave for four days recently, according to Charles Vincent, the county's construction services chief. Vincent said the inspector, a county employe for six years, has since returned to work but is no longer allowed to conduct solo inspections -- at least until the probe is completed.

Tray-Marc was the subject of an unusual state Department of Commerce hearing last month that determined the company was guilty of "gross negligence, continued incompetence and misconduct as a general contractor" and "willful failure to comply with the Virginia Uniform Statewide Building Code."

The hearing officer ordered the firm to be stripped of its state contractors license -- the first time in at least five years such an action has been taken, according to state officials.

Tray-Marc president Stephen J. Siegel, who county investigators say has moved to Florida, could not be reached for comment.

Complaints first surfaced at Tray-Marc's Montclair Country Club Lake subdivision about two years ago when homeowners reported several construction problems to the county building inspectors' office, including cracked foundations, inadequate insulation and improper grading. But Vincent said the county's one-year statute of limitations had run out on many of the alleged building code violations.

Homeowners then went to the state commerce department, which licenses and oversees contractors. Last spring, two department investigators examined more than a dozen houses and went through county inspection records. The state investigators found:

Tray-Marc filed an inaccurate application for a state license renewal last November when company officials said the firm had no lawsuits pending against it. In fact, two suits were on file at Prince William Circuit Court.

The company allowed homeowners to move into a half dozen Montclair houses even though the houses had failed inspection and the company had not obtained required occupancy permits.

Four homes had improper foundations and were structurally unsound.

Tray-Marc promised some homeowners thicker insulation than it installed.

These findings led to last month's hearing and license revocation. They also led county officials to question why the building inspectors' office had allowed Tray-Marc to carry on apparently unchecked for several years.

The result was a joint investigation by the state officials and Prince William police, who recently seized building inspection records for the subdivision.

Investigator Lagerveld, coordinator of the probe, said late last week the records show at least one building inspector approved a house foundation that was never laid and a basement that was merely a hole in the ground.

Investigators said they have found at least five such instances in the past year of work that was approved but never done. They said Tray-Marc could have used the approvals to help secure building loans or to conceal defective construction.

"Someone [in the building inspector's office] would have been very benevolent to have done this gratuitiously," said County Executive Robert Noe.

Construction Services chief Vincent said yesterday only one of his nine building inspectors, whose annual salaries range from $11,000 to $19,000, is under investigation.

But because inspectors are rotated frequently and more than one inspector approves each housing site, investigators say their probe is not limited to one person.

Noe said the potential for corruption in Prince William is real because the county is growing rapidly. Last year, the county issued 1,812 residential building permits -- more than double the 741 permits issued in 1975.