CHICAGO (CBS) — Added security and alert concert-goers.

Night two of the Foo Fighters at Wrigley Field feeling a little different after a woman said she was sexually assaulted inside a porta potty.

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Alleged assaults like the one from Sunday at such a large venue police call rare. But the underlying behavior is more common than you think.

CBS 2’s Jeremy Ross has the story.

A spokesperson for the Cubs said they are working with police on the matter. That includes reviewing surveillance video. Some call it an issue that is both criminal and cultural.

But the concern is at concerts like Lollapalooza, or when bands like Foo Fighters play Wrigley, drugs and alcohol increase and inhibitions decrease.

Lillian Cartwright of Rape Victim Advocates believes that could have played a role in the reported groping and subsequent sexual assault of a 23-year-old woman in a porta potty at the ballpark Sunday.

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Cartwright said a 2017 survey of music fans underscores the issue.

“About 50 percent of those experienced groping. It’s not shocking,” said Cartwright. “Nearly 93 percent of female fans reported experiencing some form of harassment.”

On Monday, fans found increased security near the portable restrooms. Chicago police said while reported sexual assaults like this happen from time to time, they are exceptionally rare.

Cartright said the campaign “Our Music My Body” works with festivals like Lollapalooza to avoid these kinds of incidents that can turn criminal.

“It doesn’t happen in a vacuum. It’s the harassment, the groping, the unsolicited comments that go unchecked,” said Cartright.

Authorities said they are looking for a man, approximately 45 years old, about five-foot-nine who is balding with brown hair.

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If you have any additional information on this crime, you are urged to contact Chicago police.