Several hundred vehicles were in the tunnel at the time of the fire, said Steven Winters, an acting battalion chief at North Hudson Regional Fire and Rescue.
Tunnel workers adjusted the pressure in the tunnel to keep the smoke away from the occupied vehicles and force the smoke out the New Jersey end of the tunnel.
Firefighters from North Hudson, along with Port Authority Bridge and Tunnel agents, encountered the heavy smoke as they went in to put out the fire, Winters said.
About half a dozen motorists left their cars and ran out of the tunnel, the P.A. spokeswoman said, adding that those people were located and returned to their cars.
No one was injured during the blaze, but a woman having a panic attack was treated at the scene, Winters said.
The tunnel, which was undamaged, reopened at 10:09 p.m.