Reduced staffing is contributing to rising police overtime costs, with the department using overtime to cover vacant beats, according to a report from Police Chief Howard Jordan.

Oakland is on course to spend about $16.6 million on non-Occupy Oakland-related police overtime this fiscal year -- the most since 2009 when the city instituted heightened controls on overtime costs. The city had budged $13.5 million in overtime costs for the fiscal year, which ends June 30.

The city has spent $2.8 million in police overtime on the Occupy movement, Jordan wrote in the report filed earlier this month.

Oakland has 657 police officers, far fewer than its peak of 837 several years ago. With fewer officers, police have used overtime to cover vacant beats caused by the loss of officers to attrition and a high rate of work-related injuries, Jordan wrote. Failure to backfill those beats, the chief wrote, would have resulted in longer response times.

The department loses about four officers per month to retirement and other departments, police union President Barry Donelan said. Overall police overtime spending has gone down considerably since in it peaked at $26.8 million in 2007. Last year, Oakland spent $13.5 million on police overtime.