WEST PALM BEACH, Fla. — A federal probe of tainted Chinese drywall has broadened because a small number of homeowners are reporting that American-made drywall is causing some of the same problems: a sickening, sulfurous stench and corroded pipes and wiring.

"We are not limited in the scope of our investigation to just Chinese drywall," said Scott Wolfson, spokesman for the Consumer Products Safety Commission.

The vast majority of complaints still center on China-made gypsum board. And the commission's investigation is focused mainly on the imported drywall, Wolfson said.

But sporadic reports are surfacing from owners of homes built with American drywall, and the symptoms they report are similar to those reported with the Chinese drywall: a rotten egg odor that makes occupants sick, corrosion of copper pipes, and ruined TVs and air conditioners.

"We've got a huge problem here, and we just need help," said George Brincku, 48, who bought his southwest Florida house in 2004 and almost immediately began noticing the odd smell, the corrosion of wires and headaches.

He sent samples to the Massachusetts Institute of Technology, which found that the wallboard from his home contained 50 percent gypsum and 50 percent cellulose, an organic compound. Drywall should contain mostly gypsum.

Researchers do not know for certain what causes the chemical reactions, but an MIT scientist said the mixture of gypsum and cellulose in Brincku's wallboard, combined with the humid atmosphere in Florida, were releasing sulfurous gases, causing corrosion of copper, brass and silver.