US authorities expanded a probe Monday into health impacts of drywall imported from China, saying an initial study found a "strong association" with indoor pollution in homes using the product.
The Consumer Product Safety Commission said it would be leading an investigation into the relationship between the drywall and the reported health symptoms, and electrical and fire safety issues reported by some home owners.
Some of the drywall linked to the problems was used in rebuilding in southern states after damage from hurricanes.
The agency said it would also examine the origin and distribution of the drywall, which are sheets of plaster used for home interior.
The announcement came after months of complaints from consumers and local officials that defective drywall from China was leaking chemicals that caused illness and safety problems.
"Results from a major indoor air study of 51 homes are being released today along with initial reports from two studies of corrosion in homes with Chinese drywall," the CPSC said in a statement.
"We now can show a strong association between homes with the problem drywall and the levels of hydrogen sulfide in those homes and corrosion of metals in those homes."
The agency contracted with a private health and engineering firm for the initial study of 35 homes using Chinese drywall and additional "control" homes.
CPSC said it is "leading the federal investigation and is working with other federal and state agencies to determine exactly what substances are in the drywall, what substances are emitting odors into the air and whether identified substances found in the air pose a safety or health hazard to families."
"This is a complicated investigation and the data must be evaluated before conclusions are made; nonetheless, the agencies and states involved share a sense of urgency in informing the public of their findings and developing safe and effective solutions," the statement said.
Federal and state officials had received some 2,000 complaints about the drywall for health impacts as well as corrosion of electrical components.
"We now have the science that enables the Task Force to move ahead to the next phase -- to develop both a screening process and effective remediation methods," said Consumer Product Safety Commission chairman Inez Tenenbaum.
The study concluded that hydrogen sulfide gas "is being created in homes built with Chinese drywall," although the exact methods were unclear.