Elected officials and law enforcement authorities on Sunday are expected to offer a $1-million reward for information leading to the arrest and capture of fugitive ex-cop Christopher Jordan Dorner.

A massive manhunt for Dorner began last week after the 33-year-old former Los Angeles police officer and Navy veteran allegedly began a deadly campaign that has left three people dead and two others injured. Dorner is believed to be upset over his firing from the department in 2009.

The city of Los Angeles, law enforcement organizations, private groups and anonymous donors have all contributed to the reward fund, according to law enforcement sources familiar with the investigation. Authorities have already raised $500,000 with a goal of $1 million or more.

PHOTOS: Manhunt for ex-LAPD officer

Los Angeles County Supervisors Mike Antonovich and Mark Ridley Thomas are also expected to ask the board Tuesday to contribute $100,000 toward the reward fund, according to Tony Bell, an Antonovich spokesman.

The reward announcement is expected at Sunday's 1 p.m. news conference at Los Angeles Police Department headquarters.

The news conference will be attended by law enforcement officials from Los Angeles, Riverside and Irvine, according to a statement. Officials from the FBI and U.S. marshal's office will be on hand.

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- Andrew Blankstein and Ari Bloomekatz