Media playback is unsupported on your device Media caption Minneapolis school partially collapses in explosion

A Minnesota school receptionist and janitor have died in an explosion that partially levelled the building and injured nine others, officials say.

Ruth Berg, 47, who was engaged to be married, was found by search crews in the rubble of Minnehaha Academy in the city of Minneapolis.

The body of 82-year-old janitor John Carlson was recovered on Wednesday night, hours after the blast.

Investigators suspect natural gas caused the explosion.

Image copyright Ruth Berg / Facebook Image caption Ms Berg had worked at the school for 17 years

School officials said in a Facebook post that Ms Berg had worked at the private Christian school for 17 years.

"As our receptionist, she welcomed everyone with a smile and was always willing to go the extra mile to help our students, families, and staff," they wrote.

"She will be greatly missed. Please keep Ruth's family, and our school community, in your prayers."

Of the nine injured, three remained in the hospital on Thursday, one in a critical condition, according to the Hennepin County Medical Center.

Rescuers plucked three people from the roof after the explosion, which set part of the building ablaze.

Image copyright Reuters

Mr Carlson was a 1953 graduate of Minnehaha Academy who also sent his children there, reports the Minneapolis Star Tribune.

He began his caretaker job at the school in 2003 and was known for his generosity in handing out ice cream bars to staff and students.