U.S. health officials are urging that Gulf Coast hurricane victims be moved out of their government-issued trailers as quickly as possible after tests found toxic levels of formaldehyde fumes.

Fumes from 519 trailer and mobile homes in Louisiana and Mississippi were — on average — about five times what people are exposed to in most modern homes, according to the U.S. Centers for Disease Control and Prevention. In some trailers, the levels were nearly 40 times customary exposure levels, raising fears that residents could contract respiratory problems.

The Federal Emergency Management Agency — which supplied the trailers — should move people out quickly, with priority given to families with children, elderly people or anyone with asthma or other chronic conditions, said Mike McGeehin, director of a CDC division that focuses on environmental hazards.

“We do not want people exposed to this for very much longer,” McGeehin said.

While there are no federal safety standard 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, said McGeehin.

CDC officials said the study did not prove people became sick from the fumes, but merely took a snapshot reading of fume levels. Only formaldehyde was tested, they added.

FEMA provided about 120,000 travel trailers to victims of the 2005 hurricanes Katrina and Rita. In 2006, some occupants began reporting headaches and nosebleeds.

The complaints were linked to formaldehyde, a colorless gas with a pungent smell used in the production of plywood and resins.

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.

Last May, FEMA officials dismissed findings by environmentalists that the trailers posed serious health risks. They said the trailers conformed to industry standards.

By August, about 1,000 families in Louisiana asked FEMA to move them to other quarters.

In November, lawyers for a group of hurricane victims asked a federal judge to order FEMA to test for hazardous fumes.

The CDC, working with FEMA, hired a contractor.

The firm — Bureau Veritas North America — tested air samples from 358 travel trailers, 82 park model and 79 mobile homes.