The severing of the 2-inch line was reported at about 7:45 a.m. at the property located in the 1100 block of 139th Avenue, PG&E spokesman Matt Nauman said.
No injuries were reported, but 25 employees were moved to a separate building on the property as a precaution, Nauman said.
PG&E crews responded and capped the leak shortly before 9 a.m., he said.
No injuries were reported during the incident.
The cause of the gas line rupture is under investigation, according to Nauman. He said it was possibly caused by construction work going on at the property.
Ghirardelli's headquarters and production facilities are located on the 139th Avenue property in San Leandro.