The federal government pledged Thursday to intensify its efforts to move Gulf Coast hurricane victims out of trailers and into apartments or hotels after the Centers for Disease Control and Prevention finally confirmed that many trailers were contaminated with high levels of formaldehyde.

The Federal Emergency Management Agency, which issued about 144,000 trailers to victims of Hurricanes Katrina and Rita in 2005, has been widely criticized for its slow response to extensive evidence that many trailers contain unsafe levels of formaldehyde, an industrial chemical classified as a probable carcinogen.

About 38,000 families are still living in the trailers and mobile homes, federal officials said Thursday at a news briefing, including more than 7,000 in trailer parks that FEMA had already vowed to close by May, before hurricane season begins again along the Gulf. Most of the other trailers are parked next to flooded houses that families are trying to repair.

FEMA will now hasten to move families living in trailers into apartments or, if necessary, into hotels, said R. David Paulison, the administrator of the agency.