DURHAM, N.C. -- Wednesday marks one week since a natural gas explosion in Durham killed one and left about two dozen hurt.

• At least four agencies are looking into what happened
• The city of Durham wants to piece together a time line, find out who is at fault, and the condition of the building damaged in the blast
• The agencies say there's no time frame on when their investigations will wrap up. It could take weeks or even months

At least four agencies are looking into what happened, with the two biggest questions being 'What caused a worker to cut a gas line and what ignited the explosion?'

The city of Durham wants to piece together a time line, find out who is at fault, and the condition of the building damaged in the blast.

We also know that the Department of Transportation sent an investigator from its Pipeline and Hazardous Materials Safety Administration to take a look.

The North Carolina Utilities Commission also will examine that gas pipeline and the state Department of Labor has a stake as well.

The DOL is reviewing the records and work of four companies, including Crown Castle USA, Tower Engineering Professionals, the Durham Fire Department, and PSNC Energy.

All of these companies had employees on site at the time of the blast.

The agencies say there's no time frame on when their investigations will wrap up. It could take weeks or even months.