CHICAGO (CBS) — Chicago police confiscated a Divvy bike as evidence, after it was used in a mugging overnight in the South Loop.

Police said, just after midnight, a 35-year-old woman and three friends were walking near State and Balbo, when a man rode up on a Divvy bike and grabbed the woman’s purse.

As the victim struggled with the purse-snatcher, he crashed the bike, but still managed to run away with her purse. The woman chased the robber, but soon lost sight of him.

Investigators believe the robber might have had an accomplice; a man who offered to help the victim, but was later seen with her attacker.

No one was in custody Friday morning. Area Central detectives were investigating.

Officers were seen collecting the bike as evidence. The ubiquitous blue bikes are rented from docking stations across the city.