U.S. federal investigators say a substance in drywall made in China may be causing rust and corrosion in homes across the U.S.

The Consumer Product Safety Commission released a report on Monday. It says there’s a “strong association” between the drywall and electrical problems in some newly built homes. The drywall could also be the cause of respiratory problems homeowners have reported.

The investigation was carried out after more than 2,100 homeowners across 32 states complained that their newly built homes were giving off a rotten egg odor—or that electrical systems were failing quickly.

The homes—mainly in Florida, Louisiana and Virginia—were built during a construction boom after devastating hurricanes. Since 2006, more than 550 million pounds of drywall have been imported from China to meet the construction demand.

Investigators say excessive levels of hydrogen sulfide in some of the drywall created the corrosion problem. They say it was made worse by heat, humidity, and poor air circulation in some homes.

A spokesperson for the commission says it will now look at possible ways of fixing the problems homeowners are facing.