Investigators say that at about 1:15 Monday morning, police in Tinicum Township, Delaware County, spotted the bike in a possible road race.
They followed the bike as it sped into Southwest Philadelphia.
The pursuit ended when the bike slammed into the rear of a car at Bartram and Island Avenues.
The driver of the car was not seriously injured, but the man and woman on the motorcycle have been taken to the Hospital of the University of Pennsylvania.
Both the man and the woman are in critical condition. The man had been in serious condition, but was downgraded overnight.
Their names have not been released.
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