MINNEAPOLIS — A photographer who has covered the Minnesota Twins accused Miguel Sano of assault, posting on Twitter that the All-Star third baseman forcibly attempted to kiss her following an autograph session at a mall in 2015.

Betsy Bissen tweeted Thursday that she screamed and resisted Sano until he gave up “after a solid 10 minutes of fighting.” Bissen, who has worked for publications including the popular fan blog Twins Daily , said in her tweet that she long feared that telling her story would cost her access to photograph Twins games.

Sano said he “unequivocally” denies the allegation.

“It never happened. I have the utmost respect for women, especially those working in professional sports, and I deeply sympathize with anyone who has experienced sexual harassment. There is no place for it in our society,” Sano said in a statement issued by his agent, Kyle Thousand.

Major League Baseball has begun an investigation, said MLB spokesman Pat Courtney. The Twins said they learned of the allegation only Thursday. Their statement said the team and MLB “take these allegations very seriously” but had no further comment.

In 2015, MLB and its players union unveiled a new policy covering domestic violence, sexual assault and child abuse . Commissioner Rob Manfred has the power to levy discipline, with no minimum or maximum penalty, following an investigation.

Bissen didn’t respond to an interview request from The Associated Press. She told her story on her Twitter account, writing that Sano was participating in an autograph signing at a store while she worked as a volunteer and photographed him interacting with fans during the event.

Bissen said Sano remarked that he had noticed her during games. She said he tried to flirt with her and, after the signing, grabbed her wrist and “made me go with” a small group that included Sano’s previous agent, Rob Plummer, to another store. She said she complied only to avoid causing a scene.

As the group left the mall about a half hour later, Bissen wrote, Sano said he needed to use the restroom. She pointed him to the door, and she said Sano “took that as a signal that I wanted him to grab me and try to take me back through that door.” She said she pulled back as he held on.

“It hurt, how badly he was grasping at my wrist, but he wouldn’t let go. I wasn’t going to give up my fight though. He then leaned down and tried to kiss me, more than once. Every time he did, I said no and kept pulling back,” Bissen wrote.