U.S. authorities have re-opened a major bridge in the West Coast city of San Francisco after completing repairs to a cracked section a day ahead of schedule.

The San Francisco-Oakland Bay bridge re-opened Tuesday morning as commuters returned to work following the three-day Labor Day holiday weekend. Initial traffic was light as most travelers had not expected the bridge to re-open so soon.

The 73-year-old bridge connects San Francisco with heavily-populated cities to the east. It typically carries about 260,000 vehicles a day.

Authorities had closed the bridge Thursday night as part of a separate project to replace a section of the east span with one that is better able to withstand earthquakes. Crews used the closure to inspect the bridge and found the crack.

Inspectors had planned to keep the bridge shut for repairs until Wednesday morning. But, authorities say crews worked throughout Monday night to finish the job.

Some information for this report was provided by AP.