A natural gas explosion late Wednesday morning rocked and set ablaze Minnehaha Academy’s upper school in Minneapolis, causing a partial building collapse, killing a receptionist and leaving a janitor unaccounted for while injuring at least nine others, school and emergency officials said.

School officials also confirmed the missing man as 82-year-old John Carlson, an alumnus of the school who returned in 2003 to work as a janitor and was well-loved by students and faculty alike.

A statement from school administrators said the explosion involved a natural gas leak affecting only the upper school.

Anne Dussol, who lives a block away from the school, heard the explosion.

Founded in 1913, Minnehaha Academy is a Christian school.

The academy lists several camps as being in session on during the week of July 31 the Upper School including a Girls Robotic Camp, which runs from July 31 to Aug. 4 starting at 8:30 a.m. and ending at noon.

Minnehaha Academy