SAN FRANCISCO (NewsNation) — Former champion swimmer Riley Gaines says she was ambushed and assaulted by trans rights activists at San Francisco State University (SFSU) on Thursday evening at an event where she was invited to speak.

Gaines has been an outspoken critic of transgender athletes competing in divisions in which they self-identify.

Gaines claims she was forced to barricade in a room for three hours as student protesters grew violent at the speaking event organized by Turning Point USA, a nonprofit conservative advocacy group. Turning Point’s events are frequently heavily protested at universities, and Gaines’ appearance was no exception.

Gaines said she was ambushed and “physically hit twice by a man.” The swimmer claimed it’s proof that “women need sex-protected spaces.”

If an assault did occur, it was not visible in a video Gaines uploaded to Twitter.

No arrests were reported and SFSU told NewsNation they are investigating the incident.

Gaines swam competitively against transgender swimmer Lia Thomas and has been a vocal opponent of trans rights.

On Thursday, U.S. President Joe Biden’s administration proposed schools and colleges across the country would be forbidden from enacting outright bans on transgender athletes. Teams, however, could create some limits.

That plan was immediately assailed by Republicans, who in states across the country have sought to ban trans athletes from competing in school sports that align with their gender identities.