MINNEAPOLIS — A memorial service is scheduled this weekend for the second victim of a natural gas explosion that caused part of a Minneapolis school to collapse.

Minnehaha Academy said on its Facebook page the service for 47-year-old receptionist Ruth Berg will be at 5 p.m. Sunday in the lower and middle school chapel.

A service took place last Sunday for the other victim, 82-year-old custodian John Carlson.

The National Transportation Safety Board is investigating the cause of last week’s explosion.

A spokeswoman for Hennepin County Medical Center said Wednesday the remaining person still hospitalized has been upgraded from critical to serious condition.