Contractors working on a widening project in Mission Valley struck a major gas line, sending gas high into the air over the very populated intersection of Friars Road and State Route 163.
Not only was the highway closed for hours, putting a strain on the commute overall but at least 80 businesses were closed and 1,100 homes evacuated.
A high-pressure transmission gas line pushing 400 psi was ripped open by a piece of equipment being used in the Friars Road Widening Project being managed by Caltrans.
A subcontractor working on behalf of Flatiron Construction struck the underground, 20-inch gas line.
On Thursday, a spokesperson for the Colorado-based construction company said their on-site crews responded properly once the gas line was struck.
"Flatiron crews working on site immediately activated the appropriate emergency response protocol," spokesperson Wendy Wiedenbeck said. "Flatiron is conducting a full investigation and cooperating with Caltrans as it conducts its own investigation."
The subcontractor was not named.
SDG&E spokesperson Joe Britton said the utility company has a safety program in place for construction companies to avoid incidents like the one that happened Wednesday.
"Our priority was really last night ensuring public safety and then assessing the damage and making repairs," Britton said. "We anticipate that there will be more dialogue on the cause, the precise nature of what led to this event, in the coming days."
The device doing the drilling was an auger which is shaped like a corkscrew, SDFD Battalion Chief Mike McBride said.
He said first responders cleared the initial area but soon realized the potential problem was much greater.
After that, they expanded the evacuation zone to a half-mile radius and de-energized power lines overhead.
Caltrans is conducting the investigation into what happened.
McBride also said an alert evacuating residents within a two-mile radius of the gas leak was sent in error.
Several homes and businesses were still without gas more than 24 hours after the line ruptured.
The Cheesecake Factory and about 80 other businesses in Fashion Valley remained closed and were losing business Thursday morning as SDG&E worked to restore lines to all customers.
All major restaurants in the Fashion Valley area had their service restored at about noon but other businesses and about 900 residences still did not have working gas lines, SDG&E said.
The utility company said they hoped to have all service restored by 6 p.m.