Olympic superstar Michael Phelps could face criminal charges in the fallout from a photo showing the swimmer smoking from a marijuana pipe at a University of South Carolina house party.

A spokesman for Richland County Sheriff Leon Lott, who was known for his tough stance on drugs, said on Tuesday the department was investigating.

"Our narcotics division is reviewing the information that we have, and they're investigating what charges, if any, will be filed," said Lt. Chris Cowan, a spokesman for the agency.

The photo first shown in the British tabloid News of the World on Sunday was snapped during a November party while Phelps was visiting the university, according to the paper.

Phelps, 23, and his team have not disputed the photo's accuracy. Phelps has issued a public apology, acknowledging "regrettable" behavior and "bad judgment" after the photo appeared.

One of Phelps' agents, Drew Johnson, said on Tuesday authorities had not contacted the swimmer. "So we really can't speculate," he said.

Last autumn, Phelps was introduced to large applause at a South Carolina college football game, and met with players and coaches.

Phelps also spoke at a university class on sports' role in society.

Where exactly the party occurred wasn't clear. The university said its police have no evidence it was on campus, and city police said they won't pursue criminal charges unless more information comes forward.

The Richland County sheriff can pursue charges as long as the party was in the county, the spokesman said.

"The bottom line is, if he broke the law, and he did it in Richland County, he's going to be charged," Cowan said. "And there's no difference between Michael Phelps and several other people that we arrest for the same type of a charge every day."

Under South Carolina law, possession of one ounce or less of marijuana is a misdemeanor that carries a fine of up to $200 and 30 days in jail for the first offense. Possession of paraphernalia is a $500 fine.

Meanwhile, another of Phelps's big-name sponsors - credit-payment processor Visa Inc. - said it supports him.

"We have spoken with Michael, and he has expressed regret for the situation, has committed to being accountable and improving his judgment in the future," Visa said. "We intend to support him as he looks to move forward."

On Monday, sponsors including apparel company Speedo, luxury Swiss watchmaker Omega and sports beverage PureSport's maker Human Performance Labs also said they stand behind the athlete, even if they don't condone his behavior.

(Xinhua News Agency Feburary 5, 2009)