Video (02:06) : First responders tell what it was like to arrive on scene after a gas explosion at Minnehaha Academy.

A lawsuit filed Wednesday by survivors of a woman killed in an August explosion at Minnehaha Academy alleges that CenterPoint Energy contractors “ran to save themselves” rather than warn people inside the school about a gas leak before the blast.

The Aug. 2 explosion at the south Minneapolis private school wounded nine and killed part-time custodian John F. Carlson, 82, and receptionist Ruth Berg, 47. Berg’s mother and daughter brought the lawsuit, naming CenterPoint Energy and Master Mechanical, the company contracted to move gas meters out of the building when the explosion occurred, as defendants.

The lawsuit alleges that CenterPoint and Master Mechanical made several critical mistakes that day to cause the explosion, which occurred when fall classes were not yet in session. Neither CenterPoint nor a team from Master Mechanical told school officials about the “high degree of danger” posed from moving the gas meter, according to the suit filed in Hennepin County, which asks for at least $50,000 in damages.

They also failed to close shut-off valves disconnecting the supply line from the old meter, causing gas to flow into a confined pit area where it would accumulate and explode, the lawsuit says. NTSB investigators have said they were focusing on the source of the leak that caused the explosion.

“The employees and agents of the Defendants, and each of them, who were responsible for the meter relocation project ... committed a series of blatantly unsafe, unreasonable and otherwise highly dangerous acts with deliberate disregard for the rights or safety of others,” the lawsuit alleges.

A National Transportation Safety Board (NTSB) report said two workers evacuated the area after failing to contain the gas leak.

The explosion Aug. 2 at the Minneapolis school wounded nine and killed part-time custodian John F. Carlson and receptionist Ruth Berg.

According to the lawsuit, the workers “immediately realized that explosive conditions existed.

“However, rather than alerting building occupants and people in the vicinity of the building of the danger and the need to take immediate action, the employees and agents of the Defendants, and each of them, ran to save themselves and ignored the safety of others, including Plaintiffs’ decedent, Ruth Berg.”

Fred Pritzker, an attorney representing Berg’s family, said he was only aware of the two Master Mechanical employees being at the site that day, but no supervisors from CenterPoint.

Pritzker said the explosion could have easily been prevented, “just by shutting off the gas stream.”

A school maintenance worker heard and smelled the natural gas release, and went to the basement meter room where the workers had been. After realizing the danger, the worker got on his radio to tell other staff members to evacuate the building immediately, before racing upstairs to warn others, the report said. Less than a minute later, the building exploded, the NTSB said.

In a statement, Master Mechanical officials said they are reviewing the lawsuit.

“Out of respect for the various ongoing investigations, we will not be discussing the details at this time,” the statement said. “We continue to actively cooperate with all state, local and federal agencies investigating this tragic event. We ask that you continue to keep in your thoughts and prayers all those affected by the incidents.”

CenterPoint Energy spokesman John Ward said, “Our plan is to respond during the course of the legal process.”