Reversing his earlier claims, Park Tae-hwan has said he may have heard about a banned substance in the contested injection that led to his positive doping test, a legal statement showed Thursday.

Park, suspended after testing positive for testosterone, had earlier claimed he didn't know he received a hormone shot at a Seoul clinic until after learning the doping test results. The head doctor at the clinic has been indicted on the charge of professional negligence.

However, in an affidavit submitted to the Seoul Central District Court for the doctor's hearing on Thursday, Park said, "I think (the doctor) may have spoken about male hormones" before he received the injection in July last year.

The former Olympic champion was slapped with an 18-month ban in March, retroactive to last September. Prosecutors asked Park to testify as a witness at Thursday's session, but the swimmer said he would attend another hearing in the future, citing his training schedule. The next hearing has been set for July 14.

In the same affidavit, Park also said that while he knew steroids were banned substances, he had no knowledge that testosterone was also prohibited in competitions.

At a press conference on March 27, his first public appearance since the ban was handed down, Park maintained that he wasn't properly informed of the injection's contents.

Park also said he had visited the hospital to treat a skin condition, contrary to rumors that he went to increase his hormone level.

Park, prohibited from training at national facilities under international swimming anti-doping rules, began training at a public pool in Seoul on Monday. (Yonhap)