Police on Thursday were investigating a pursuit that ended in a fatal crash in Los Alamitos overnight.

Officers were responding to a call in the City of Cypress when the pursuit began, the Los Alamitos Police Department stated in a news release.

The vehicle they were chasing eventually crashed into a building in the 4000 block of Katella Avenue.

An unidentified bystander was struck and killed in the crash, police said.

Two people, believed to be the driver and passenger of the pursuit vehicle, were detained and are being questioned by investigators.

The identities of the detained individuals have not been released.

A SigAlert was issued for the shutdown of a portion of Katella Avenue near the crash site during the investigation.

There was no word on what prompted police to begin the pursuit.