OAKLAND -- Police are warning the public to use extra caution near Highland Hospital following a daytime sexual assault Wednesday.

A 54-year-old woman was walking in the 1300 block of East 31st Street around 12:25 p.m. when she was approached by a stranger, pulled into a secluded area and groped, police said. The man attempted to further sexually assault her, but the victim got away and called police.

The woman was not physically injured.

The suspect is described as a black man between 25 and 35 years old, standing 5 foot 10 and weighing about 140 pounds with unknown hair color and eye color. He was wearing a black shirt, black pants and black boots, police said. Police said the man walked away after the assault.

Crime Stoppers of Oakland is offering a reward of up to $5,000 for information leading to an arrest. Anyone with information should call the youth and family services division at 510-238-3641 or a tip line at 510-637-0298 or the Crime Stoppers of Oakland tip line a 510-777-8572.

Follow Kristin J. Bender at Twitter.com/kjbender.