The city declared two Oakland apartment buildings unsafe for human occupation yesterday, and gave the residents of the 24 units until Monday to find new homes, as Pittsburgh Mayor Luke Ravenstahl used an aggressive new tactic in response to concerns about code enforcement.

Using a power rarely invoked, the city's Bureau of Building Inspection posted signs saying, "Dangerous, Keep Out," on 331 and 337 McKee Place. After the tenants -- mostly students -- leave, the owners won't be allowed to rent out units until the code violations are fixed.

An inspector distributed notices with the phone number of the University of Pittsburgh's off-campus housing arm, and the mayor reached out to Pitt to help relocate the students.

Acting Chief of Building Inspection Dan Cipriani said his inspector cited the properties in 2006 and is "getting no cooperation" in fixing the violations.

"We've taken this unique step to really show that we're serious about this," said Mr. Ravenstahl. "Enough is enough."

At 311 McKee, inspectors in 2006 found mysterious gas odors, insufficient smoke detectors, doors with inadequate fire resistance, windows that don't open and piles of junk under the fire escape. The property is owned by Dormont-based Elrod Investments, run by Jason Cohen.

"Since 2006, this owner has failed to correct the problems," said Public Safety Director Michael Huss. "This person has gotten away with this for far too long."

Yesterday, residents of the building seemed shocked at the city's sudden action. Former tenants weren't surprised.

Angela Collins, a Pitt graduate who moved out of the building last year, said it was a dump.

"The front door, the lock never worked," she said. "The floors were sagging in. There were apartments that had huge holes in the wall ... . There were huge puddles all over the stairs whenever it rained. The fire escape looked like it was going to fall off. It was a joke between our friends in school."

When her radiator broke, "it took them a solid year to fix it," she said. "We had cockroaches."

Mr. Cohen could not be reached for comment. Nor could Century 21 Progress Realty, which receives mail for 337 McKee owner Hosny Sayed Abdel Latif, according to the inspection bureau.

At 337 McKee, the lack of fire-resistent doors, walls and ceilings was cited on the bureau's shutdown notice.

Mr. Ravenstahl's action comes days after two Oakland residents, Laura M. Rosato and Nathan Hart, called for an Office of Municipal Investigations probe into code enforcement. Both wrote that Senior Building Inspector Robert McPherson told them that citations "have been removed from [case] files" and "are not making it to housing court," as Mr. Hart put it.

Mr. McPherson "is really doing a great job," said Mr. Hart, president of the Oakland Community Council. "We just want to see where in the chain the breakdown is."

When Mr. Cipriani asked Mr. McPherson about the comments, he learned of the outstanding fire code violations and told Mr. Huss, who ordered the shutdowns.

Mr. Huss said there is a paperwork bottleneck in the process that slows the transfer of housing code cases to the district judges who hear them. He said a new computer system set to be up and running by mid-year should get cases to court faster.

Yesterday, District Judge Gene Ricciardi ordered another company controlled by Mr. Cohen to submit to a building inspection tomorrow of 3408 Parkview Ave., also in Oakland. "If that is not done, there's going to be hell to pay," he said.

City inspectors filed a case involving that property in January after a lengthy effort to get violations fixed.

The Pittsburgh Post-Gazette reported on numerous building code violations in student housing in 2006, prompting city action that started under Mayor Bob O'Connor and continued under Mr. Ravenstahl. Two Oakland students died in apartment fires in 2006.