CHICAGO (CBS) — More gunfire on a Chicago expressway.

But this time, Illinois State Police found no victim, no shooter but only shell casings.

It happened on the Dan Ryan near 75th around 4:30 Wednesday morning. ISP said Chicago police called after receiving a ShotSpotter report of gunfire.

Investigators found three casings. The 71st Street ramp was closed for about an hour.

There have been no arrests.