Wisconsin State Fair Park officials are instituting some changes following at least two dozen arrests and injuries to park police officers during opening day of the fair.

State Fair Park CEO Rick Frenette says about 24 people were arrested on the grounds Thursday during disturbances on the midway. Frenette says seven park police officers were injured, including two who were taken to the hospital.

Frenette says there will be an increased police presence following disturbances at the fair and surrounding neighborhood. And, he says all those under 18 attending the fair will have to be accompanied by a parent or legal guardian after 5 p.m.

Milwaukee and West Allis police are investigating reports of a crowd of young people injuring at least four people as they left the fair.

Wisconsin Valley Fair officials say they aren't too worried about violence in central Wisconsin.

Fair administrators say the Wausau Police Department and the sheriff's office are on hand throughout the weekend, but so far the crowds have been behaving themselves.

"We bring on extra security at night during the grand stand shows and they do a really good job at just making sure the crowds are maintained and they do a really good job or policing the fairway, policing the Grandstand and just looking out for something that could go wrong."

Saturday’s band, Sick Puppies performed in the Grandstand.

The fair is open all day Sunday until 8 p.m.

The Associated Press contributed to this story