CenterPoint Energy hired the company to move the gas meter from inside the building to the outside to get easier access, KARE 11 said.
NTSB Chairman Christopher Hart described moving the meter as a "very hazardous operation," the Star Tribune says, adding they're investigating what may have gone wrong or if the workers were tired or impaired prior to the explosion.
A memorial service for Carlson was held Sunday, KARE 11 says. A service for Berg has not yet been announced.
Nine others were injured in the incident. And as of Thursday, all but two people had been released from the hospital.
Funds set up for the school
The first day of school at Minnehaha Academy's Upper School, where the explosion happened, has been delayed by two weeks. Kids were supposed to start Aug. 23, but now they'll begin Sept. 5.