MINNEAPOLIS _ Federal investigators arrived Thursday morning at Minnehaha Academy's upper school, where a natural gas leak a day earlier ripped a huge gash into the center of the building in south Minneapolis, killing two staff members and injuring nine others.
Among the many aspects of the explosion being investigated is whether workers turned off the gas inside the building, rather than at the street, and what role that might have played in the incident, according to Minneapolis Assistant Fire Chief Bryan Tyner.
"We are looking at everything, including that," Tyner said. "One of the things we'll be looking at is what those contractors were doing."
According to city records, Eagan-based Master Mechanical Inc. was issued a permit June 7 for "gas piping and hooking up meter" at the address. Ryan Larsen, a financial officer with the company, said soon after the blast, "We've got people on the site there. They are figuring it out."
Workplace inspections of Master Mechanical have led to two citations for violations in recent years, neither yielding major penalties, said Jenny O'Brien, a spokeswoman for Minnesota OSHA. One violation involved an employee falling at a Bloomington site. In 2014, it was cited for paperwork violations at a Maple Grove site.
Also Thursday, administrators met throughout the day at Minnehaha's lower school to determine where classes will begin for the upper school students, given that instruction is scheduled to begin Aug. 23.
"None of those plans have been made whatsoever," said Minnehaha facilities director Curt Bjorlin. "We're just starting preliminary meetings on what's going to happen. No decision has been made."
The Christian school had an enrollment of 825 for both schools combined in 2015-16. Asked whether the lower school many blocks to the south could absorb the upper school students, Bjorlin said, "I doubt it."
Damage to the school is extensive. The building, on West River Parkway, collapsed mostly in the center portion, where the utility area is located. Window frames were popped out of walls. Classrooms also took the brunt of the blast. Two floors collapsed over a subbasement, which quickly filled with water from the firefighters' hoses used to battle the blaze.
The natural gas explosion killed receptionist Ruth Berg, 47, and part-time custodian John F. Carlson, 82. Fire officials said the two bodies were found near each other, both on the south side in the collapsed portion of the building.
A full-time custodian, Bryan Duffey, was in the same area and critically injured. Duffey, who has been with the school for a year and also is an assistant boys soccer coach for Minnehaha, is being treated at Hennepin County Medical Center. Two others remain at HCMC and were in satisfactory condition Thursday.
Bjorlin described Duffey as a "nice guy and hard worker, with a good heart."
Duffey is a 2013 graduate of Northwestern College in Iowa, where he played soccer. His wife, Jamie Duffey-Jeltema, graduated from the same Christian liberal arts school a year earlier.
A rapid-response team from the National Transportation Safety Board was at the school Thursday morning to investigate the leak.
The agency's team, whose overall responsibilities include investigating transportation and pipeline accidents, said it planned to brief the news media sometime Thursday afternoon. The NTSB does not announce causes of accidents while on the scene. Rather, the agency says, such determinations can take a year or more before being reached.
Although the Bureau of Alcohol Tobacco and Firearms initially sent agents to the scene, the agency won't be involved in the investigation since the source was the explosion was a natural gas leak, said spokeswoman Ashlee Sherrill.
Fred Pritzker, a Twin Cities attorney who has filed dozens of lawsuits following explosions across the country, said the investigation will focus on cause and origin _ trying to identify the source of the gas and how it ignited.
"This is not the type of thing that happens in the absence of negligence: Somebody screwed up big time," Pritzker said. "The financial exposure is likely to be shared by more than one entity."
"Whenever you've got an older building, you're always looking to see if these were capped off lines and if they were pressurized," he said.
Pritzker said investigators would also try to determine who was working in the area of the leak, and whether they were properly trained. "A lot of times you've got people who are working around a gas line who have no business doing so," he said.
To determine the source of the leak, investigators may "re-pressurize" the gas line with a nonexplosive gas, he said.
"It could be a gas line, it could be an appliance that was leaking, it could be any number of things," he said. "We don't know if this was a sudden large escape of gas or if this was a slow escape of gas."
John Purdy, a former boiler inspector, says the building's age may have played a role. "If you've got a shut-off valve, you can't trust that it'll close on you, if it hasn't been closed in a while," he said.
Along with year-round staff tending to their summertime responsibilities, several athletic teams were practicing at the upper school when the blast rocked the building and could be heard many blocks away.
Firefighters responded to the call around 10:30 a.m., and there was some confusion about the address of the building, according to emergency dispatch audio communication.
"It looks like it could have been an explosion," one firefighter reported over the radio. "We have windows that were blown out on the west side of the building ... we also see now flames and fire and a building collapse as well."
Staff and parents at the Christian school along the Mississippi River gathered together to grieve Wednesday night, even as they gave thanks that fall classes were not yet in session when the blast occurred.
"Tonight is an example of the kind of caring community we are," Minnehaha Academy President Donna M. Harris, who was injured in the explosion, said during the prayer service at the academy's lower and middle campus. "We're going to get through it. We trust God. He is going to do phenomenal work."
On Thursday morning, neighbors and curious residents strolled and stopped by the explosion site. In the drizzling rain, they pulled out their phones to take photos of the rubble.
Jim Norman, 70, stopped in front of the fencing overlooking the soccer field and school behind it. He graduated from Minnehaha Academy in 1965 and remembered seeing John Carlson at school sporting events.
Losing him and Ruth Berg "is a tragedy," he said, wearing a black Minnehaha Academy cap.
The bonds to this school are strong, he said. His wife, brothers and two sisters also graduated from here. To see the building reduced to debris is "shocking."
"From the looks of this structure, it's all gonna have to be torn up," he said.
Carolyn Bedingham and her daughter Ellie, of Woodbury, were returning from a trip to Colorado and were unable to attend Wednesday evening's vigil. So they stopped by Thursday morning with Ellie's friend Laura Shea to place a bouquet at the foot of the fence overlooking Minnehaha Academy.
Ellie and Laura have gone to Minnehaha Academy since preschool and are soon starting their senior year. They held back tears as they looked at what remained of the halls they used to roam.
"I didn't realize how bad it was until I saw it," Ellie said. "You could've been standing up those stairs when it exploded. When you think about that, it's hard."
