Teamsters who work at American Red Cross blood services facilities in Philadelphia are on strike.
Rocky Bryan of Teamsters Local 929 says they're striking over what the union says are problems with working conditions.
The union says lengthy work hours and pay cuts create fatigued workers more prone to mistakes when transporting blood. They say high job turnover means that workers are less experienced.
The workers set up a picket like early Thursday outside the Red Cross headquarters in Philadelphia.
Red Cross officials could not immediately be reached.