Friday an ATF spokesperson said investigators are interested in the center of the damaged building.
Although the investigation is underway, teams have not been able to enter the building. Officials said half of the building may have to be demolished in order for it to be safe to enter.
- 911 communications examined
- Victim's family frustrated
- Click here to read background information about the deadly explosion
- Click here to see images from the scene
"There's nothing that we will not be looking at," said Earl Woodham, ATF.
The first priority for investigators -- going into the unstable ConAgra Foods plant -- will be a challenge.
"The building is not safe at all, I don't know how else to describe it," said Frank McLaurin, Search and Urban Rescue Team.
Woodham said they must secure the building before investigators are allowed to enter.
"The number one thing we will do is we will make the building safe before we commit anybody else's life to this investigation," he said.
While the property is being secured, the ATF will interview workers, administer polygraphs and conduct forensics tests.
The U.S. Chemical Board will try to determine what caused the explosion and the fire that eventually caused portions of the plant to collapse.
Officials said the investigation will be treated as a criminal investigation until the possibility of foul play is ruled out.
Meanwhile, there are hundreds employees who worked at the plant and need assistance.
ConAgra announced a United Way Relief Fund and donated $100,000.
Click here to learn more about the fund or to make a donation electronically or by check
You may also call (919) 463-1367.
The company also said it will continue to pay its Garner workers indefinitely.