Updated 11:55 p.m. ET

An apparent gas explosion and partial building collapse at a private school in Minneapolis on Wednesday has left two people dead and nine people injured, according to the local fire department.

The school, Minnehaha Academy, says on Facebook that the one of those who died was a receptionist at the academy and the other was a custodian, whose body was recovered after a search into the evening.

The academy announced on Facebook Wednesday night that the second person killed was John Carlson, who had graduated from the school in 1953 and returned to work there after his retirement.

Earlier the school had identified the first person killed as Ruth Berg, who had worked there for 17 years.

School officials also announced that all summer program students "are accounted for and safe." Contractors were reportedly working on the building at the time of the explosion.

Tim Nelson of Minnesota Public Radio reports:

"The blast leveled the center of a building at the upper school at Minnehaha Academy.

"School spokeswoman Sara Jacobson says classes were not in session, but there were students and staff in the building at the time: 'The students who were here on site were practicing basketball in the gym ... at the far northern side of the building,' [she said.] 'The explosion happened in the middle of the building. They certainly could feel the rumble, but there was no impact to them personally.'

"At least three of the injured were initially listed in critical condition and four others in serious condition following the blast."

MPR also reports that the campus chapel was packed Wednesday evening for a prayer service.

Minnehaha Academy is a private, Christian college prep school, located on the banks of the Mississippi River in Minneapolis. The explosion happened at the academy's Upper School campus, for students in grades 9 to 12.

The Associated Press has more on the apparent cause of the explosion:

"The Minneapolis Fire Department says a gas explosion caused the blast and partial building collapse Wednesday at Minnehaha Academy. Fire officials say contractors were working on the building at the time.

"Assistant Fire Chief Bryan Tyner ... says three people were rescued from the roof, and another person initially believed missing was found unhurt."

The Star Tribune reports that the explosion involved a gas leak:

"The natural gas supply from CenterPoint Energy was cut off, and the utility has 'well-trained, experienced crews on site who are coordinating with local emergency officials to secure the area,' said company spokeswoman Becca Virden. 'We will conduct an investigation to determine the cause.'

"Along with the blast taking out a significant chunk of the building, walls still standing had their window frames popped out.

"According to city of Minneapolis records, Eagan-based Master Mechanical Inc. was issued a permit on June 7 for 'gas piping and hooking up meter' at the address.

"Ryan Larsen, a financial officer with the company, said, 'We've got people on the site there. They are figuring it out.' "

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