The Federal Emergency Management Agency will step up efforts to move Gulf Coast hurricane victims out of more than 35,000 trailers now that tests on some of those trailers indicate possibly high levels of formaldehyde, the agency's chief said Thursday.

David Paulison made the announcement at an afternoon news conference, after the Centers for Disease Control said fumes from 519 tested s and mobile homes in Louisiana and Mississippi were — on average — about five times what people are exposed to in most modern homes.

In Louisiana, there are 25,162 occupied FEMA trailers. In Mississippi, there are 10,362, according to FEMA figures. Other state also have hundreds of trailers. At one time, FEMA had placed victims of the 2005 hurricanes, Katrina and Rita, in more than 144,000 trailers and mobile homes.

Paulison and Dr. Julie Gerberding, director of the CDC, said they hope to get people everyone out of the trailers before the warm summer months, when heat and a lack of ventilation in the trailers could make formaldehyde accumulations worse.

Trailer occupants will be moved to apartments or hotels. If necessary sturdier mobile homes — pre-tested for formaldehyde — will be used, he said.

"The real issue is not what it will cost but how fast we can move people out," Paulison said.

Paulison also said FEMA would never again use travel trailers to house disaster victims but may continue to use larger, better constructed mobile homes.

Commonly used in manufactured homes, formaldehyde can cause respiratory problems and has been classified as a carcinogen by the International Agency for Research on Cancer and as a probable carcinogen by the U.S. Environmental Protection Agency.

While there are no federal safety standards for formaldehyde fumes in homes, the levels found in the trailers are high enough to cause burning eyes and breathing problems for people who have asthma or sensitivity to air pollutants, Mike McGeehin, director of a CDC division that focuses on environmental hazards said prior to the news conference.

Gerberding said the levels of formaldehyde in the tested trailers varied widely. Some levels were low. In some trailers, the level would be enough to cause breathing problems for children, the elderly or people who already have respiratory problems. About 5 percent had levels that could cause problems for people who do not ordinarily have respiratory problems, she said.