BEIJING — Olympic champion Michael Phelps has apologized to Chinese fans for what he called his regrettable behavior after he was photographed with a marijuana pipe.

Chinese media on Thursday quoted the swimmer saying he had made amends to his Chinese fans via the Internet.

"To all my Chinese friends, I made a mistake and did something which I deeply regret. However, I am deeply comforted by all the messages of support and encouragement posted on the Chinese Internet," Phelps was quoted as saying by the Beijing Youth Daily newspaper.

"This incident has taught me an important lesson and I vow to swiftly change my attitude, train in the best athletic spirit, and make you all proud of me once again."

Last month Phelps was back in Beijing — where he won a record-breaking eight gold medals — to do commercials and endorsements for automaker Mazda, which is reported to be paying him more than $1 million to endorse the brand in China.

Like most of his major sponsors, Mazda is apparently sticking with Phelps as a spokesman. However, the Kellogg Co. has cut ties with Phelps, saying it had made a business decision not to extend his endorsement contract. The cereal and snack maker said Phelps' behavior was "not consistent with the image of Kellogg."

Chinese papers have followed the Phelps controversy closely, dubbing it "marijuana gate."

"Over the past few years, China has left a deep impression on me, and I am a great admirer of your history and culture," Phelps said. "I look forward to visiting China again and thank all of my Chinese fans for your messages of support, encouragement, and understanding. ... I am sorry for letting everyone down and promise not to let such a thing happen again."