A spokesman for Richland County Sheriff Leon Lott, who is known for his tough stance on drugs, said yesterday that 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.
Visa said yesterday that it supports the 23-year-old, but Kellogg Co. and Subway did not return calls to The Baltimore Sun. A Kellogg spokesman told the Associated Press that it declined to comment.
On Monday, Speedo, Omega watches, Hilton Hotels and PureSport said they stand behind Phelps but did not condone his behavior.
The photo first shown in the British tabloid News of the World was snapped during a November party while Phelps was visiting the university, according to the paper.
Phelps has not disputed the photo's accuracy. He issued a public apology, acknowledging "regrettable" behavior and "bad judgment" after the photo appeared.
Drew Johnson, one of Phelps' agents with Octagon, his management firm, said yesterday that authorities had not contacted the swimmer. "So we really can't speculate," he said.
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 1ounce or less of marijuana is a misdemeanor that carries a fine up to $200 and 30 days in jail for the first offense. Possession of paraphernalia is a $500 fine.
The Richland County sheriff has long sought to fight drug crimes. Lott rose from patrol officer to captain of the narcotics division in the early 1990s, after the television series Miami Vice made its splash.
Lott played the part well. He wore stylish suits and had long hair then. He drove a Porsche seized from a drug dealer and even worked undercover with federal agents in Florida.