By Chris Kenning
(Reuters) - U.S. safety investigators began a weeklong inquiry on Friday into a fatal explosion at a Christian private school in Minneapolis, including examining whether workers moving a gas meter could have caused the blast.
National Transportation Safety Board investigators planned to speak to contractors on Friday, agency spokesman Terry Williams said. The NTSB, which investigates accidents involving pipelines, previously said it would examine a wide range of potential factors, including worker training.
The Wednesday morning explosion at Minnehaha Academy caused part of the school building to collapse, killing two staff members and injuring nine other people.
Master Mechanical Inc was issued a permit for gas piping and hooking up a meter in June, according to city documents.
The company had no immediate comment on Friday. It said in a statement to local media on Thursday that its employees were among the injured.
The Minnesota Occupational Safety and Health Administration cited Master Mechanical in 2014 for two violations, including failing to develop a training program for employees exposed to hazardous substances, agency documents show.
Jenny O'Brien, spokeswoman for the state agency, said such violations were considered routine.
Minnehaha Academy receptionist Ruth Berg and custodian John Carlson were killed by the blast that tore through the Upper School, officials said.
On Friday, Bryan Duffey, an assistant soccer coach at the school, remained in critical but stable condition at the Hennepin County Medical Center, the hospital said. One other person was listed as satisfactory a day earlier, but no information was available on Friday.
Minnehaha Academy was founded in 1913 and teaches more than 800 students from pre-kindergarten through 12th grade on two campuses, according to its website.
School was not in session on Wednesday due to the summer break. City fire officials said the situation would have been far worse if students had been in class.
(Reporting by Chris Kenning; Editing by Lisa Von Ahn)