New Jersey State Police Sgt. Brian Polite says an accident involving at least two vehicles occurred around 4 p.m. Thursday near Clark.
Polite says at least one person suffered serious injuries and was airlifted to University hospital in Newark.
All northbound lanes have been reopened and at least three southbound lanes are now open.
Police say traffic was backed up for at least 20 miles on the southbound side of the parkway, between Clark and Bloomfield, as of Thursday evening.
Polite says a preliminary investigation indicates that one vehicle may have rear-ended another in the southbound lanes near Interchange 135.