Police sought clues after witnesses reported seeing occupants of two cars exchanging gunfire in a Pasadena neighborhood on Friday morning, authorities said.
The incident took place about 10:20 a.m. in the 900 block of North Raymond Avenue, according to Pasadena police Lt. Anthony Burgess.
Witnesses reported seeing two cars chasing one another as gunshots were fired, he said.
Officers found spent bullet casings at the scene, but no signs of any suspects or victims, Burgess said.
Police scoured the area in search of the involved vehicles, but they were not found.
No further details were available as the investigation remained in its early stages.
Anyone with information can reach the Pasadena Police Department at (626) 744-4501. Tips may also be submitted anonymously to L.A. Regional Crime Stoppers at (800) 222-8477.