OAKLAND –Two men were wounded multiple times in a drive-by shooting Monday morning in West Oakland, authorities said.

The men, one 18 and the other 21, were in critical but stable condition at a hospital.  Both men are Oakland residents, and police said they are friends.

The shooting, which prompted the activation of a gunshot detection alert system, happened around 12:57 a.m. Monday in the 800 block of Filbert Street.

According to initial police reports, the  21-year-old man was sitting in his parked car and his friend was standing outside the vehicle.  A vehicle drove by and at least two occupants began shooting at the men, according to the reports.

The vehicle and suspects fled before police got to the scene. The wounded men were transported from the scene by ambulances.

Dozens of shell casings were recovered in the area.

A residence was also hit by some bullets, but no other injuries were reported, police said.

A motive for the shooting is under investigation.  Detailed descriptions of the shooters and vehicle they were in have not been released.

Anyone with information about the shooting may call investigators at 510-238-3426.