At least 16 people were injured on Thursday when seven vehicles crashed inside San Francisco's Bay Bridge tunnel.
Multiple eastbound lanes were closed after the collisions which happened around 12:40pm local time, officials said.
A long queue of traffic could be seen after the crash.
Two of the people injured were hospitalised, though their injuries appeared minor, officials said.
Also read|US: TV meteorologist, pilot die in news helicopter crash
All 16 people who were either taken to hospitals or treated at the scene were expected to recover, they added.
The fire department had earlier said that 18 people were injured, and four of them had been transported to a hospital.
However, they later issued revised figures.
All of the lanes were re-opened shortly after 2pm.
Details about what caused the pileup were not immediately known.