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(CNN) — South Korean football team FC Seoul has apologized after fans accused the club of using sex dolls to fill empty stands at its second game of the K League season.

On Sunday, the club played at home against Gwangju in South Korea’s top football championship, which was due to start on Feb. 29 but was postponed because of the coronavirus pandemic.

Fans were barred from the ground as part of measures to prevent the spread of infection, but those watching online noticed something off-color about the mannequins drafted in to fill the stands.

Some of the figures were holding signs for a company that makes sex dolls, and fans pointed out that they looked like adult dolls rather than mannequins.

“Honestly, if you saw the mannequins you should have thought they were strange,” wrote one fan on Instagram.

Others were incredulous that no one at the club had noticed the issue.

“The female mannequin dressed in a white short sleeve t-shirt, the breast excessively stood out, and the nipples were protruding, but you didn’t know they were an adult product?” wrote another fan on Instagram. “You are kidding me.”

In response, the club issued an apology on Instagram and Facebook.

“Regarding the cheer mannequins that were installed during the game on the 17th, we sincerely apologize for causing deep concern to the fans,” the statement said.

FC Seoul explained that although the dolls were made to look like real people, rather than conventional mannequins, it had checked they were “not at all related to adult products” before agreeing to install them, and had been told they would be mannequins of the kind commonly used to model clothes.

Staff “went through the confirmation process that they were not adult products several times,” said the statement, and didn’t notice that an ad for adult products was visible on the day of the game.

“This is our fault without excuse,” said the club. “Regardless of the reason, we apologize again for causing great concern to the fans who love and cheer for FC Seoul.”

CNN has attempted to contact the club for further comment.

The South Korean K League is one of just a handful of football leagues still functioning after the world game was largely shut down by the pandemic.

Germany’s Bundesliga also restarted this weekend, with teams playing in empty stadiums.

Other leagues are grappling with the question of restarting competitions that were postponed.

Some football authorities, including those in France, have decided to cancel the 2019/2020 season.

However, the UK’s Premier League, Spain’s La Liga and Italy’s Serie A are still considering their options.