Mary Ann Schultheis displays the black dust that is covering the copper tubes in the air conditioner Wednesday in the second story of her Parkland, Fla., home, while speaking about the problems that she is having with her house. Chinese drywall was used in the construction of her house and is now causing problems, including corroding copper pipes and wiring, and causing the house to smell. Some officials believe the only way to solve the problems is to remove the walls, studs, and wiring. She had the house on the market for sale, but she is taking it off until she finds a way to correct the problems.

Parkland, Fla. ? At the height of the U.S. housing boom, when building materials were in short supply, American construction companies used millions of pounds of Chinese-made drywall because it was abundant and cheap.

Now that decision is haunting hundreds of homeowners and apartment dwellers who are concerned that the wallboard gives off fumes that can corrode copper pipes, blacken jewelry and silverware, and possibly sicken people.

Shipping records reviewed by The Associated Press indicate that imports of potentially tainted Chinese building materials exceeded 500 million pounds during a four-year period of soaring home prices. The drywall may have been used in more than 100,000 homes, according to some estimates, including houses rebuilt after Hurricane Katrina.

“This is a traumatic problem of extraordinary proportions,” said U.S. Rep. Robert Wexler, a Florida Democrat who introduced a bill in the House calling for a temporary ban on the Chinese-made imports until more is known about their chemical makeup. Similar legislation has been proposed in the Senate.

The drywall apparently causes a chemical reaction that gives off a rotten-egg stench, which grows worse with heat and humidity.

Researchers do not know yet what causes the reaction, but possible culprits include fumigants sprayed on the drywall and material inside it. The Chinese drywall is also made with a coal byproduct called fly ash that is less refined than the form used by U.S. drywall makers.

Dozens of homeowners in the Southeast have sued builders, suppliers and manufacturers, claiming the very walls around them are emitting smelly sulfur compounds that are poisoning their families and rendering their homes uninhabitable.

“It’s like your hopes and dreams are just gone,” said Mary Ann Schultheis, who has suffered burning eyes, sinus headaches, and a general heaviness in her chest since moving into her brand-new, 4,000-square foot house in this tidy South Florida suburb a few years ago.

She has few options. Her builder is in bankruptcy, the government is not helping and her lender will not give her a break.

“I’m just going to cry,” she said. “We don’t know what we’re going to do.”

Builders have filed their own lawsuits against suppliers and manufacturers, claiming they unknowingly used the bad building materials.

The Consumer Product Safety Commission is investigating, as are health departments in Virginia, Louisiana, North Carolina, Florida and Washington state.

Companies that produced some of the wallboard said they are looking into the complaints but downplayed the possibility of health risks.

“What we’re trying to do is get to the bottom of what is precisely going on,” said Ken Haldin, a spokesman for Knauf Plasterboard Tianjin, a Chinese company named in many of the lawsuits.

The Chinese ministries of commerce, construction and industry and the Administration of Quality Supervision Inspection and Quarantine did not respond to repeated requests for comment. Chinese news reports have said AQSIQ, which enforces product quality standards, was investigating the complaints but people in the agency’s press office said they could not confirm that.

Meanwhile, governors in Louisiana and Florida are asking for federal assistance, and experts say the problem is only now beginning to surface.

“Based on the amount of material that came in, it’s possible that just in one year, 100,000 residences could be involved,” said Michael Foreman, who owns a construction consulting firm. The company has performed tests on some 200 homes in the Sarasota area and has been tracking shipments of the drywall.

Federal authorities say they are investigating just how much of the wallboard was imported. Shipping records analyzed by the AP show that more than 540 million pounds of plasterboard — which includes both drywall and ceiling tile panels — was imported from China between 2004 and 2008, although it’s unclear whether all of that material was problematic or only certain batches.

Most of it came into the country in 2006, following a series of Gulf Coast hurricanes and a domestic shortage brought on by the national housing boom.

So far, the problem appears to be concentrated in the Southeast, which blossomed with new construction during the housing boom and where the damp climate appears to cause the gypsum in the building material to degrade more quickly. In Florida alone, more than 35,000 homes may contain the product, experts said.

Outside the South, it’s harder to pinpoint the number of affected homes. And in drier climates such as California and Nevada, it may be years before homeowners begin to see — and smell — what may be lurking inside their walls.