Southbound Highway 101 in Burlingame reopened about 2:30 p.m. Saturday, long hours after construction equipment slammed into an electrical tower Friday night.

One lane of northbound Highway 101 will remain closed, however, as crews continue their work, the California Highway Patrol said.

Drivers had to use alternate routes through the area, including Interstate 280 and El Camino Real. The California Highway Patrol said Pacific Gas and Electric Co. had to bring in special equipment to de-energize the power lines, and PG&E had crews dealing with the damaged tower. No injuries were reported, according to the CHP.

Motorists were stranded on the freeway for hours after the accident.

The trouble started at about at about 9:30 p.m., when the back of an excavator operated by a Caltrans contractor doing construction on the Highway 101 Broadway Interchange Project hit an electric transmission tower that carries power to the Peninsula and San Francisco, PG&E and Caltrans officials said. The excavator was drilling into the ground and pouring concrete at the time, then turned and hit the tower, Caltrans officials said.

The mishap dropped four electrical transmission lines onto the freeway. Power momentarily flickered for miles around, including at AT&T Park during the Giants game Friday night, PG&E said. Drivers near the live power lines on the freeway were ordered to stay inside their vehicles as a safety precaution and remained there until around 3 a.m., when PG&E was able to shut down the power lines, utility spokesmen said.

There were no outages reported, as PG&E was able to quickly re-rout power through other transmission lines. No service interruptions were expected as the transmission towers area were repaired Saturday.

As of Saturday morning, utility workers were waiting for the excavator to be removed from the area before they could decide what needed to be done and complete the repairs at the tower site, they said. Utility workers also need to see if two nearby towers were damaged in the incident, company officials said.

Traffic was heavy both on city streets around the accident site and on Highway 101 and other nearby freeways.

Hamed Aleaziz and Henry K. Lee are San Francisco Chronicle staff writers. E-mail: haleaziz@sfchronicle.com, hlee@sfchronicle.com Twitter: @henryklee, @haleaziz