The investigation into the causes of the Minnesota bridge collapse may take as long as 18 months, the US National Transportation Safety Board says.
Thousands of people came to see the wrecked bridge at the weekend
But while the exhaustive inquiry is set to last until 2009, computer technology may mean quicker answers than in past bridge collapses, officials say.
Debris from the eight-lane bridge, which collapsed at evening rush hour on 1 August, still blocks the Mississippi.
Five people have been confirmed dead and eight are unaccounted for.
Meanwhile, a state highway has been converted into a freeway in a bid to reduce commuter traffic disruption around Minneapolis following the destruction of what was the city's busiest bridge.
The timing of traffic signals has also been changed, new turn lanes have been created and access roads have been closed, while more city buses are running and car pooling is being encouraged.
The state authorities hope to begin moving the debris from the river later this week.
Investigators will use hi-tech software to simulate removing a key support structure, examining how the bridge reacts.
The investigation may feature a helicopter with a high-resolution camera to peer into the wreckage, laser-guided surveying equipment to produce an in-depth map of the debris and software re-creating the disaster on a computer screen, the Associated Press reports.
Such technology should produce answers much faster than when crews had literally to piece together fallen bridges in the past.
"Computers and modelling techniques are just light years from what was available 40 years ago," Ted Galambos, a structural engineering professor at the University of Minnesota, told the agency.
"Now we can have an idea and we can test that on a computer in a few hours."
No estimated completion time was given for the river-clearing operation which has the twin aim of helping the recovery operation and opening the Mississippi to river traffic again.
State officials have said they hope to have the bridge rebuilt by the end of next year.
Divers are due to return to the river later on Monday to search for the eight people reported missing. They have requested help from FBI and Navy teams.
Funerals for three of the victims are scheduled for later this week.
Memorial services were held at the weekend for the dead and missing who include a pregnant nursing student and her toddler daughter.
Another missing person, Christine Sacorafas, who was stuck in a traffic jam on the bridge when it fell down, was remembered by her priest at a church service.
"We don't know where she is," the Rev Richard Demetrius Andrews said at the end of the service in St George Greek Orthodox Church in St Paul.
"As far as I know, they have not even found her car. This is a very agonising time for the family, not knowing her status. Not knowing if she's alive, not knowing if she's injured or how badly."