The difficult job of extracting tons of broken concrete, metal bridge beams and submerged cars from the Mississippi River was moving forward this morning, six days after the Interstate Highway 35W bridge suddenly collapsed.

Divers were scheduled to head back into the river to search for the missing, possibly with help from the FBI and Navy dive teams.

City residents, meanwhile, faced the challenge of commuting into downtown without a major freeway.

The bridge had carried up to 140,000 vehicles a day before it fell in the river Wednesday evening during rush hour. Cars tumbled into the swift current and onto broken concrete, killing five people and leaving eight missing and than 100 people injured. Five people remained hospitalized in critical condition Monday morning.

NTSB Chairman Mark Rosenker said the city had been given permission for a contractor to begin removing the bridge remnants, a long and costly process that will begin with the staging of four cranes and then the start of the removal. Inspectors will examine the removed debris to determine exactly where and why the bridge came apart.

“It will be tough work but also sensitive work,” Minneapolis mayor R.T. Rybak said today on CBS’s “Early Show.”

Sunday was a day of prayer for the dead and missing. An estimated 1,400 people filled St. Mark’s Episcopal Cathedral for an interfaith service, marking what Gov. Tim Pawlenty described as the start of the healing period.

“We’re here to begin the process of restoration,” he said.

The Rev. Peg Chemberlin, executive director of the Minnesota Council of Churches, told the crowd that though they came in “shared anger and anguish,” the city had rallied in crisis.

“It’s important that we stand together and say, ‘Minnesota, your heart is full of courage and compassion,”’ she said. “The heroes in this moment, like the tears, are many.”

Ahmed Sahal Iidle, father of Sadiya Sahal, a pregnant nursing student who was missing with her toddler daughter, was joined by about two dozen other Somali Muslims in brief prayers Sunday night at the Brian Coyle Community Center.

They prayed for the protection of the searchers and the speedy recovery of the missing. They also announced the Somali community will hold a public memorial service for all the victims Friday.

Funerals for three of the dead were scheduled for this week.

Clearing the bridge wreckage will help with the recovery operation and open a channel at least 56 feet wide to accommodate barge and boat traffic.

For commuters, traffic patterns have been reconfigured and a state highway has been converted into a temporary freeway to help prevent major bottlenecks. Other changes were being made in the timing of traffic signals, locations of turn lanes, closing of access roads and addition of buses. The city encouraged carpooling and asked commuters to leave home earlier than usual if possible to stretch out the morning rush hour and ease congestion.

The National Transportation Safety Board said it could take as long as 18 months to complete its investigation into why Minnesota’s busiest bridge collapsed and fell into the river. They will use high-tech software to simulate removing key support structures to see how the bridge reacts.

“If they remove a piece and it falls down the way they saw it, that’s a pretty good indication they found the right piece, and there’s all sorts of ways of doing that,” said W. Gene Corley, senior vice president of CTL Group, an engineering firm.

Corley, who has helped investigate bridge collapses, as well as disasters such as the attacks on the World Trade Center and the Oklahoma City federal building, predicted federal officials would have a pretty good idea of the cause within a few weeks.

State officials said they hope to be able to have the bridge rebuilt by the end of 2008. Pawlenty said Sunday the cost could be as high as $350 million. The clean up is expected to cost as much as $15 million.