When William Murray moved into his apartment near Capitol Hill in August, his landlord assured him that the unit was free of lead paint, asbestos or any other hazard.

But a month later, the owner informed city officials that all 46 units at the Lincoln Terrace Apartments, including Murray's, had to be vacated because of dangers posed by lead paint and asbestos. The tenants were given 120 days to leave.

Murray was perplexed and angry.

"I can't believe one month later there's lead paint," said Murray, who works for a publishing distributor. "I think it's part of a scheme. I realize we're in the Capitol Hill area. They're trying to build condos."

For the tenants, the order to vacate was an introduction to a little-known District law, 501 F of the Rental Housing Act, that allows landlords to temporarily empty buildings if planned renovations and repairs present a safety hazard to the tenants. Although the law guarantees tenants the right to return, an acceleration in landlords' use of the provision has raised concern among tenant advocates. They say it is yet another tool to turn affordable housing into luxury units in the city's many gentrifying neighborhoods.

Under the law, tenants have an "absolute right" to reoccupy apartments after repairs are made, and they can return at the same rent if the repairs are meant to bring the building into compliance with the housing code. But the law does not place a time limit on repairs, which in some cases can take years and consequently reduce the likelihood that a tenant would return.

This year, city officials have received requests to vacate 13 buildings, totaling 443 units. In 2003 and 2004, requests were received for eight buildings.

At two recent hearings before the D.C. Council's Committee on Consumer and Regulatory Affairs, chaired by Jim Graham (D-Ward 1), tenants in Murray's building described the owner's tactics, which included a late-night visit from a representative who offered $500 immediately if tenants signed papers agreeing to move out in four months and $500 more once the building was emptied. Some tenants said they were not told by the owners that they could move back into their apartments at the same rent after the repairs.

Murray's building and several others that have received similar notices are owned by Perseus Realty LLC, which initially received approval to vacate the properties from the D.C. Department of Consumer and Regulatory Affairs. But the approval was based on a lead and asbestos study done for a building in Leesburg. The city official who signed the order to vacate, rent administrator Raenelle Humbles Zapata, told Graham's committee that she rescinded it when she realized the error.

Patrick J. Canavan, director of the regulatory agency, told Graham's committee that the rent administrator's work was "sloppy" and said steps would be taken to have experts available to inspect buildings for toxic materials. The regulatory agency is responsible for enforcing rent control and reviewing and ruling on requests from building owners to remove tenants before doing major repairs.

Woody Bolton, a partner with Perseus Realty, acknowledged that a mistake was made but denied any intentional wrongdoing. Bolton said that Murray's building, on 16th Street NE, contains asbestos and lead and that Perseus has reapplied for permission to vacate it as well as three others that initially received approval: two on Vernon Street NW in Adams Morgan and one on T Street NW in Shaw.

Bolton said that tests were done in June and July on all four buildings and that the correct study will be submitted to city officials. He said the buildings need structural repairs that would create a hazardous condition for tenants because asbestos and lead will be released into the air.

"The only intention we have is to make a safe living condition for the residents," Bolton said. "That's 100 percent of our strategy."

During the hearing this week, Graham asked Bolton how much the owner planned to spend on renovating the four buildings. Bolton said the work would cost about $125,000 to $185,000 a unit, depending on the repairs.

Graham, who did his own calculations from the dais, noted that the owners would be investing $14 million on the four buildings. Sounding incredulous, he asked Bolton whether tenants would still be charged the same amount in rent, as required under law.

Bolton replied affirmatively and acknowledged that it could be 10 to 20 years before the owners realized a return on the investment.

Graham, who has asked for a review of all recent requests by landlords who are invoking the law, said that its use in gentrifying neighborhoods is worrisome and could lead to unscrupulous acts, such as tenants not being told that they have the right to return at the same rent.

"This is a way to hoodwink people out of valuable property," Graham said. "Once the apartments are cleared out, they will come on the market for a lot of money."

Earlier this year, Graham led an effort to close a loophole that allowed property owners to bypass a city law that gave tenants first rights to purchase a building. Graham said he believes the sudden popularity of the 501 F section of the housing rental act signals that property owners have found another legal strategy to clear out buildings, including some units covered by rent control.

W. Shaun Pharr, a spokesman for the Apartment and Office Building Association of Metropolitan Washington, said he was unaware of any abuse of the law.

"Responsible housing providers will not be using lead-based paint or any other conditions as a subterfuge for moving people out," Pharr said. "Certainly Mr. Graham has a right to investigate these recent instances, but when you think about the fact that there are 150,000 units of rental properties in the city, there's clearly not a widespread conspiracy to subvert tenants' rights."

Residents of the apartments where William Murray and his daughter Trudy live have been told to vacate because of lead paint and asbestos.