The Milwaukee County Sheriff's Office is investigating three incidents of lewd behavior and one sexual assault in the area of Lincoln Park along the Oak Leaf Trail.
According to officials, one victim was able to fight off the suspect.
The area is being patrolled by the sheriff's office.
The sheriff's office also shared some tips for staying safe when you're out on the trail.
"Have someone walk with you. If that's not available, walk your dog," said Capt. Paul Thompson with Milwaukee County Sheriff's Office. "Another thing people could do is to let someone know that they're walking on the trail."
Although officials didn't say what time of day the incidents happened, they said it's generally best to use the trail during daylight hours. If you're out after sunset, stay in well lit areas.
If you are attacked, Capt. Thompson said you can fight back if you're able and call 911 as soon as you can.
Anyone with information is asked to contact 414-278-4788.