WASHINGTON -- In testimony before a Congressional committee investigating potential dangers of ephedra-based diet supplements, NASCAR President Mike Helton revealed on Thursday that the racing series has added the controversial stimulant to a list of substances it looks for when it tests competitors for drugs.

Although NASCAR has not followed other leagues' lead in prohibiting competitors from using ephedra, Helton told the House Energy and Commerce Committee that "at some point, it may be appropriate to make our policy more specific."

Ephedra, linked to reports of as many as 100 deaths, has been banned by the NFL, NCAA, Olympics, MLS and minor league baseball.

Its use is still allowed in Major League Baseball, the NHL and NBA, and the U.S. government does not restrict its sale to the general public.

NASCAR spokesman Jim Hunter said the series has been testing drivers and crewmembers for about two months.

In a March 26 USA TODAY story, cited by a committee member during Thursday's hearing, one racing team's trainer estimated that 80% of NASCAR crewmembers had tried ephedra. Helton said Thursday that he believed that estimate "wasn't quite accurate" and said NASCAR hasn't yet had a competitor test positive for excessive ephedra use.

But unlike the NFL, which conducts random, unannounced drug tests of all its players, NASCAR's substance abuse policy provides for testing only if there is "reasonable suspicion" that a driver or crewmember might be using banned substances; NASCAR has conducted about 10 drug tests since it began looking for ephedra.

Rep. Janice Schakowsky, D-Ill., questioned Helton for NASCAR's sending of what she called "dual messages" to its fans by testing competitors for ephedra, but also accepting advertising from Stacker 2, a product line that includes ephedra supplements.

Helton explained that Stacker 2 sponsors a racing team, not NASCAR, but acknowledged that most fans don't make that distinction.

Helton said NASCAR officials have discussed the sponsorship with team owner Bill Davis, and that those conversations "will take on possibly a different light."