A report released Friday by the Centers for Disease Control and Prevention finds four Michiana manufacturers of travel trailers and mobile homes whose units, used for Hurricane Katrina and Rita victims, have significantly higher than normal levels of formaldehyde.

The CDC issued the results after testing of the housing units contracted by the Federal Emergency Management Agency in the wake of the Gulf Coast disasters.

FEMA requested the tests in July, following numerous disaster victims' reports of illness and a class action lawsuit filed in May 2006.

The interim findings show Gulfstream, Keystone, Pilgrim and Forest River — all manufactured housing firms based in Elkhart County — had higher than normal levels of formaldehyde.

The four companies are among six firms that provided 61 percent of the units used in a category that includes travel trailers, mobile homes and the manufactured park model. The CDC said because Gulfstream travel trailers are the brand FEMA used most, the study reflects higher numbers of those units.

The research, done in December and January, included 519 manufactured housing units.

The temporary homes were selected at random from a list of nearly 47,000 that were still occupied in Mississippi and Louisiana in November, the CDC said in its report.

In each unit, air samples were taken for one hour, under the residents' normal sleeping conditions, to determine the formaldehyde levels. Research staff also measured humidity and indoor temperature, and did not permit smoking or cooking while taking the samples.

They also looked at general home conditions, including mold, and followed up with a resident questionnaire.

The four brands showed significant elevations beyond the normal level of U.S. exposure, which is between 10 and 30 parts per billion in indoor air, the CDC reported.

The most frequently high levels were found in Gulfstream travel trailers. The Nappanee-based company had 14,624 units listed with FEMA and 121 in the sample, with an average reading of 103 ppb. The Gulfstream products showed 56 percent of its travel trailers in the sample had levels equal to or greater than 100 ppb.

Keystone, based in Goshen, had 1,395 units listed, with 53 percent of the 38 sampled reading at 100 ppb or greater. For Pilgrim International in Middlebury, there were 1,584 units listed, and 51 percent of the 39 sampled had formaldehyde levels at or higher than 100 ppb.

And the units from Forest River, an Elkhart-based firm with 3,200 units listed, showed 44 percent at that level among 39 sampled.

The CDC said there is no specific number that defines safe levels from dangerous ones, and all manufacturers had at least some units showing elevated readings.

But as the level rises, people may have symptoms — and there may be an increased risk of cancer even at levels too low to cause signs of any illness.

In fact, the CDC suggests that the formaldehyde-level results may actually be lower than levels the hurricane victims are exposed to because lower temperatures and humidity lead to a decrease in the exposure.

The agency stressed an urgency to moving displaced hurricane victims, with whom they are meeting this week in Mississippi to discuss the report and its findings. The CDC has been notifying people of results since February 21.

The final report on the study is expected later in spring.