Nearly 40 homes were destroyed and at least four people were killed last week in the San Bruno neighborhood.
Three people are still listed as missing, authorities said. They all lived at the same address, just yards from the source of the blast.
Schwarzenegger held a news conference and was briefed individually by city, state and federal officials, at least one of whom prompted the governor to wipe tears from his eyes.
Speaking from a vantage point overlooking a massive crater and destroyed homes, Schwarzenegger credited emergency personnel and others for what he termed their "quick action" in responding to the explosion and fire.
Schwarzenegger promised a thorough investigation into the events leading up to the explosion.
"I will make sure that we get every single detail," he said. "I'm back now and I'm going to drill down into that information."
When asked why he did not end his trip to Asia and return immediately to California, Schwarzenegger said he trusted Lt. Gov. Abel Maldonado, a fellow Republican and the state's acting governor while Schwarzenegger was out of the country.
The governor also said that the day after the explosion he spoke to President Barrack Obama by telephone and requested a federal disaster declaration.
Besides Schwarzenegger and other local officials, Pacific Gas & Electric Co. President Chris Johns was also at the scene Wednesday.
Johns said that manual valves, like the ones workers had to manually shut in order to close off the flow of natural gas in the pipeline, are used by utility companies nationwide.
Johns also suggested that heavy traffic might have contributed to a delay in getting the valves closed after the explosion.