FARGO (AP) - United Blood Services of North Dakota says it has a critical shortage of a number of blood types.

Recruitment director Jennifer Bredahl said the agency is short on types O negative, O positive, B negative and B positive. She says United Blood Services is seeking donors at its blood centers in Bismarck, Fargo and Minot, and in Aberdeen, S.D., or through community blood drives.

The nonprofit organization serves hospitals in North Dakota, western Minnesota and northern South Dakota.