Three Boston police officers and two other people were taken to Boston Medical Center with injuries not believed to be life-threatening Friday after two separate car crashes involving police cruisers, the Boston Police Department said. Police are investigating a crash involving a police cruiser and another car at around 6 p.m. at the corner of Harvard and Warner streets in Dorchester, the statement said. Two officers and one other person were injured. Around 7:30 p.m., an officer and the driver of a motorcycle were injured when their vehicles collided at the corner of Langdon Street and Norfolk Avenue in Roxbury, police said.Todd Feathers can be reached at firstname.lastname@example.org. Follow him on Twitter @ToddFeathers.