Approximately 1,200 Baltimore workers were to return to work today at a downtown municipal office building, two days after they were sent home because gasoline fumes had seeped from the ground into the air inside the building.
Construction of a nearby subway tunnel, which is apparently forcing the fumes from the ground, was halted while the state's Mass Transit Administration worked to eliminate the noxious odor inside the building.
A city spokesman yesterday said the fumes, which may be coming from underground gasoline storage tanks, "have greatly improved" but that environmental officials will continue to monitor the problem all day today. There is no threat of an explosion, the officials maintain.
Mayor Kurt L. Schmoke sent city workers home at noon Monday, nearly a week after employees began complaining about the fumes.
James L. Kapplin, city public works spokesman, said the workers at the 14-story Charles L. Benton, Jr. Building at 417 E. Fayette St. were to return today, but that there would be a "liberal leave policy."
"That means if there is some odor in some offices and somebody feels uncomfortable, they can go home," Mr. Kapplin explained.
State environmental officials have said the gas was being forced into the building by nearby construction of the 1.5 mile-long Metro extension from Charles Center to Johns Hopkins Hospital. The fumes are "weathered gasoline," wafting from the basement and the walls of the Benton building, which houses the city's transportation, planning and housing departments, as well as the elections board and zoning permit office.
Caryn Coyle, spokeswoman for the state's Department of the Environment, said the source may be underground storage tanks left from a gasoline station dating to 1955.
"Right now that seems to be the most logical cause," said George G. Balog, city public works director. He also said the highest concentration of fumes is coming from the area where the old gas tanks were located.
Officials said they believe the fumes were forced into the building from compressed air being used to keep ground water out of the subway tunnel under East Baltimore Street, adjacent to the Benton building.
"We have stopped tunneling temporarily simply as a precaution," said MTA spokeswoman Dianna Rosborough. She said the air pressure in the tunnel has been reduced.
MTA contractors have also drilled sink holes to ventilate the Benton building and have sealed cracks in the floors and joints of the building to keep the fumes out, she said.
Ms. Rosborough said she did not know when subway construction under East Baltimore Street will resume.