The organizer of the 2016 Shanghai International Marathon, one of the most significant sporting events in China, has asked 20 athletes from China to pay back a total of $1,438 in taxes from their prize money.

Two months after this year's races, event organizer East Best and Lansheng Group said it forgot to withhold tax from prize money it issued to some winners.

The incident does not involve foreign participants because they have yet to be issued prize money until the International Association of Athletics Federations announces the results of anti-doping tests.

"Our financial department made a mistake," said Zhou Jin, executive deputy secretary-general of the Shanghai International Marathon Organizing Committee. "The prize money given to winners should have been subject to a tax deduction, but the financial department was in a transitional period, which led to the mistake."

Zhou said the committee has apologized to the athletes involved and are communicating with them to resolve the issue. "We are grateful that they have shown understanding and a willingness to cooperate."

This year's Shanghai Marathon took place on Oct 31 and about 38,000 athletes participated, including foreigners. In addition to the grand prize of $45,000 for the full-marathon winners, the event organizer also gave prizes to athletes who finished in the top eight of both the full and half-marathon races.

With the prizes being issued in phases, the miscalculation took place in the most recent round of payouts.

Zhou said the committee has reached an agreement with the tax authority, so that any losses will be covered by the committee if athletes do not pay back the requested amounts.

The incident came to light after Li Shaozhuang, who won $400 for his fifth-place finish in the half-marathon, said on social media on Monday that he was concerned that he would be blacklisted by the organizer if he declined to pay back 20 percent of his prize money.

In a later interview with Beijing News, Li said he would ask the organizer to provide a tax sheet. The organizer agreed to this request, with Zhou adding that athletes can transfer the money after they receive tax bills.

She also said prize money for foreign athletes would be issued after tax deductions through their designated agency when all formalities are completed.