The incident was reported at about 9:20 a.m. at Brittan Avenue and Industrial Road, San Carlos fire Chief Doug Fry said.
A construction company apparently hit a 2-inch gas line, causing the rupture, he said.
PG&E crews capped the gas line within an hour, Battalion Chief Mike Gaffney said. No injuries were reported.
No evacuations were ordered but those in the area were initially told to stay indoors, he said.
"The risk was not as significant as it could have been (because) the gas was able to travel straight into the air and dissipate" due to a lack of wind, Gaffney said.
The intersection was closed for nearly an hour.