Charlotte, NC- Investigators say the explosion that killed a 4-month-old baby and sent both her parents to the hospital was most likely an accident.

Natural gas is the most likely cause, and the man who smelled it hours before the explosion says he’s horrified his call for help didn’t do more.

Robert Massey says he was outside enjoying a quiet evening with his dog Jojo when he says a powerful odor — one that was unmistakable — came his way.

“I got a strong whiff of natural gas,” Massey said.

He called 911.

“The fire department came out, they went in the back, they checked my meter, (and) they didn’t find anything,” Massey said.

He thought everything was OK.

“They left, I went back to sit back in the swing with JoJo and all of a sudden ‘Boom!'” Massey said.

Seven houses down, the house exploded, most likely because of natural gas, firefighters said.

Charlotte’s fire chief says his guys checked Massey’s house, the two on either side and the one across the street. The only thing they found was a gas grill with a propane tank.

“They did a pretty thorough search, found what could have been a cause of an odor and eliminated that and then cleared the scene,” Chief Jon Hannan

The same crew of firefighters was back on the same street less than two hours later trying to find the body of 4-month-old Synora Coleman.

“I was pretty upset, especially after I learned the 4-month-old child was in there, and I didn’t sleep too good last night either,” Massey said.

The chief arson investigator says they expect to release the exact cause Monday