Residents started to return to their California neighborhood on Sunday after it was decimated by a gas explosion last week.
Officials still want to know what went wrong and they have ordered Pacific Gas and Electric to inspect all of its natural gas lines across the state.
Residents being let back into their San Bruno homes were escorted by utility crews who turned on the electric power and gas. Many of the people say they are still traumatized by last week's deadly fire.
"My biggest concern is my 6-year-old and making sure that she is comfortable," said resident Steve Hoff. "She hasn't been sleeping well the last couple of nights, just small noises and different things."
"My heart goes out to my neighbors and the lives lost. I'm really shocked at what I'm seeing right now," resident Walter McCaffrey said.
"It's not just the physical reconstruction," said San Bruno Mayor Jim Ruane. "It's the mental reconstruction that's going to have to take place that's going to affect our city and our individuals and our citizens for many, many years to come."
Investigators have discovered some clues about what might have caused the blast.
At the time of the rupture, PG&E was in the middle of a federal inspection program -- looking at gas transmission lines that ran through high consequence areas. Four leaks were found among those pipes.
"When you realize that some of this pipe was laid in 1948 -- others in the 50's -- it raises a lot of questions," said Sen. Barbara Boxer, D-Calif.
Even as some families began returning to their damaged homes, officials are still trying to confirm just how many people died as a result of the blast and resulting inferno.
The remains of at least four people have been found. Officials said four others are still missing and at least 60 people were injured, some critically.
"It's really hard to put into words the way you feel when you see a beautiful neighborhood and a whole section of it that just almost disappeared, and the remnants of the cars melted in the driveways," Boxer said.
Meanwhile, investigators are looking into reports by some residents that they smelled gas several days before the explosion.