The swimmer under police scrutiny.

Olympic swimming champ Michael Phelps has apologized for a photo depicting him using a bong, but one South Carolina sheriff says police can't let the incident slide without an investigation.

"If someone breaks the law in Richland County [of Columbia, South Carolina], we have an obligation as law enforcement to investigate and to bring charges," Sheriff Leon Lott Jr. said in a statement to People.com.

The Web site says the controversial photo of Phelps, 23, was snapped in Columbia last November.

"The Richland County Sheriff's Department is making an effort to determine if Mr. Phelps broke the law," continues Lott. "If he did, he will be charged in the same manner as anyone else. The Sheriff has a responsibility to be fair, to enforce the law and to not turn a blind eye because someone is a celebrity."

In a statement to ET, Phelps -- who won a record eight gold medals at the Beijing Games -- conceded the authenticity of the exclusive picture published Sunday by the tabloid News of the World. The photo depicted Phelps smoking from a water pipe, commonly referred to as a bong, which is frequently used to smoke marijuana.