A woman walking along the Charles River in Waltham was reportedly assaulted Sunday night, according to Massachusetts State Police who are trying to track down the suspect.

The woman in her 20s was walking on the footbridge between Newton Street and Farewell Street near Shaw’s at around 8 p.m., she told police.

The woman then heard footsteps come up from behind, and she was reportedly grabbed by someone who tried to put his hand over her mouth, according to State Police.

The woman screamed, and the suspect let go of her and ran off.

She described the suspect as a man in his 30s or 40s, with tan skin, average height and with athletic build. He was wearing a baseball hat.

Units from Mass State Police and Waltham Police responded and searched the area, but they were not able to find the suspect. The investigation into the assault remains active.

“We urge the public to be aware of their surroundings and the presence of other people around them when walking in any public space,” a State Police spokesperson said in a statement.

“People should carry a cell phone, don’t wear headphones, and may also consider carrying pepper spray,” the spokesperson added. “If you see anything our anyone suspicious call 911 immediately. If you are assaulted, if at all possible scream, make noise, and fight back.”