( CNN ) -- A South Carolina sheriff 's office is investigating whether Olympic gold medalist Michael Phelps smoked marijuana on the University of South Carolina campus . Michael Phelps is facing a criminal investigation into whether he smoked marijuana on a college campus . Authorities will file criminal charges if the investigation determines that they are warranted , a spokesman said Tuesday . `` If someone breaks the law in Richland County , we have an obligation as law enforcement to investigate and to bring charges , '' Sheriff Leon Lott said in a statement . `` The Richland County Sheriff 's Department is making an effort to determine if Mr. Phelps broke the law . 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 . '' Phelps admitted `` regrettable behavior '' on Sunday after a British newspaper published a photograph of him smoking through a bong . The tabloid News of the World showed Phelps using the bong during what it said was a November party at the University of South Carolina , in Richland County . Both university police and Columbia , South Carolina , police have said they would not pursue charges , according to The State newspaper in Columbia . It was unclear where the party took place , the paper said , or whether it was on the USC campus . `` I engaged in behavior which was regrettable and demonstrated bad judgment , '' said Phelps , who won a record eight gold medals at the 2008 Olympic Games in Beijing , China , in a statement Sunday . See the photo on the cover of Star magazine » . `` I 'm 23 years old , and despite the successes I have had in the pool , I acted in a youthful and inappropriate way , not in a manner that people have come to expect from me , '' he said . `` For this , I am sorry . I promise my fans and the public -- it will not happen again . '' The U.S. Olympic Committee also issued a statement that said in part , `` Michael has acknowledged that he made a mistake and apologized for his actions . We are confident that , going forward , Michael will consistently set the kind of example we all expect from a great Olympic champion . '' In 2004 , Phelps was arrested on charges of driving under the influence in Salisbury , Maryland . He pleaded guilty and was sentenced to 18 months probation . He also issued an apology after that incident . Phelps is one of 12 Olympic athletes who have signed on to `` My Victory , '' an initiative launched last year by the U.S. Anti-Doping Agency aimed at keeping competitive sports clean .
Charges will be filed if warranted , sheriff 's spokesman says . Tabloid published photo it says was taken at University of South Carolina . Photo shows Phelps with a water pipe used for smoking pot . Phelps apologized over weekend for `` regrettable behavior ''