National Transportation Safety Board officials are leading the investigation of the natural gas explosion that killed one person and demolished buildings in Canton.
NTSB Investigator Ravi Chhatre says it may take a year for the agency to issue a report. The NTSB investigates pipeline accidents that involve fatalities, substantial property damage or significant injury.
Canton Police Chief Rick Nichols says local authorities welcome the federal assistance. The city is allowing some businesses on the downtown square to reopen this afternoon.
But authorities say three properties, including the historic Opera House, have been condemned as a result of the blast. Chief Nichols says 48 other buildings in the downtown area were damaged but can be fixed.
Ameren Illinois authorities have said the explosion occurred while utility workers were trying to fix a gas leak that a contractor for a communication company apparently caused when installing fiber-optic cable.
The explosion killed Ameren worker Arturo Silva Jr. of Mapleton, who was on a crew called to repair the line. Three other Ameren workers and several other people were injured. Officials have said the other injuries are not life-threatening.