The Terrace Tunnel on State Highway 1 in Wellington is open again after being checked for a suspected gas leak.
The Fire Service says it did a sweep of the tunnel using gas detection equipment and could find no trace of a leak.
The tunnel was closed during rush hour on Monday morning when motorists reported smelling gas, but is now considered safe.
Gas lines company Powerco says the smell may have been LPG from a vehicle. It is doing a second round of testing to rule out the possibility of a gas mains leak.
