MINNEAPOLIS -- Investigators have three more videos showing the area around the Interstate 35W bridge at the time it collapsed that they hope will shed light on the disaster.

That was the word from National Transportation Safety Board Chairman Mark Rosenker on Friday afternoon in Minneapolis. He said the videos were turned over to the FBI by the U.S. Army Corps of Engineers and were subsequently handed to the NTSB for investigation.

There were actually four videos recorded by Army Corps security cameras, one showing the bridge collapsing that has already been shown on television, one more that shows the collapse from another angle and two that were directed away from the bridge, Rosenker said.

The NTSB is beginning to do computer modeling of the area around the bridge in hopes of shedding light on its collapse, he said. He said the investigation so far has shown the southern edge of the bridge shifted 50 feet after its collapse.

Rosenker said that despite earlier reports, the investigation would not involve reconstructing the collapsed bridge. He said the pieces from the bridge will eventually be moved down river and investigators will be matching up the pieces to find the ones that provide the most clues.

"Our objective is do to a thorough, orderly investigation without cutting corners," he said. "But we also want to open the river as soon as possible for the people of Minneapolis."

Conditions Better Than Expected

Better than expected conditions in the Mississippi River have aided in the search at the scene of Wednesday's deadly bridge collapse in Minneapolis, officials said Friday afternoon.

Hennepin County Sheriff Rich Stanek said four of the five submerged vehicles inspected were found to be empty. One of the missing victims whose car was among those underwater was found safely.

The fifth vehicle was crushed under another car and was on the bottom of the river.

Hennepin County Commissioner Mark Stenglein said the sight of the collapsed bridge is "beyond sobering."

"It's a very, very sad, sad sight," he said. "Our city is cut in half."

County sheriff's department Capt. Bill Chandler said that the dive teams have trained for this type of situation.

"There are very distinct, methodical ways of doing things," Chandler said. "The conditions are slightly better than we thought there would be."

Chandler wouldn't speculate on whether cars -- and perhaps their occupants -- were on the bottom of the river under the deck of the bridge. Chandler said the divers were not being allowed to search that area due to safety concerns.

"We don't know how many cars were on the bridge and how many people were in the cars," Stanek said. "It will take time -- more time than we've had thus far."

The recovery effort had recovered no bodies Friday, Minneapolis Police Chief Tom Dolan said at a 3 p.m. CDT press conference.

Dolan said authorities are keeping numbers close to their vests until they are more concrete.

"If you are off, if you're high or low, you need to explain the difference," he said. "As time goes on, we'll be more comfortable with letting that information out."

He said that there are 30 vehicles visible to crews right now and that estimates predict there would have been another 20 to 30 vehicles on the bridge at the time of its collapse.

However, he said word from divers at the scene is that there might not be that many vehicles in the water, with the number closer to 15 vehicles. They continue to search the river and are reporting that some of the vehicles are stacked, Dolan said.

Fifth Victim Confirmed

The Hennepin County medical examiner's office confirmed early Friday that a fifth body had been recovered overnight.

The Minneapolis Star Tribune reported that firefighters pulled the driver of a tractor-trailer, which was engulfed in flames in the collapse, from the wreckage late Thursday, fire department spokeswoman Kristi Rollwagen said.

Dr. Andrew Baker, Hennepin County's Chief Medical Examiner, said the identity of the truck driver would be announced once the family is notified.

Stanek said Friday morning that eight people are missing, a number revised down from 30 on Thursday.

Stanek said that 16 boats would be back on the river. Thanks to the Army Corps of Engineers, the water level of the Mississippi River has been lowered to make it easier to see debris in the water.

Dolan said authorities had been in contact with the family of at least one victim who was pinned in the wreckage and spoke with rescue workers before dying. That victim's family members said they did not want the details of that conversation released to the public, he said.

As crews continue to explore the river, the rubble both above and below the water is serving as a net and will likely collect any victims from upstream, he said.

"With a little bit of bad luck it could have been much, much worse," he said. "If that school bus had gone in it could have been catastrophic and it is already catastrophic for the families involved."

Dolan also told the media that the wide perimeter around the scene would be kept in place while the recovery efforts are ongoing. He said there was a discussion of providing a visit to the scene for the media, but that the recovery effort and visits by first lady Laura Bush and President George W. Bush prevented that.

"We have a very dangerous scene there," Dolan said. "We also have a water recovery effort with a lot of sensitive things that could happen. As far as the scene itself, the perimeter is where it needs to be."

On Thursday, the office released the names of the four who were earlier confirmed dead in the accident:

Sherry Lou Engebretsen, 60, of Shoreview, who died of multiple blunt-force injuries.

Julia Blackhawk, 32, of Savage, who died of blunt-force trauma.

Patrick Holmes, 36, of Mounds View, who drowned.

Artemio Trinidad-Mena, 29, of Minneapolis, who died of blunt-force injuries.

There were at least 80 injured, according to Dr. John Hick of the Hennepin County Medical Center.

First lady Laura Bush is in Minneapolis Friday and President George W. Bush is also expected to visit the site Saturday. (Read More: First Lady Meets With Bridge Responders )

Bridge Inspections Ordered

The U.S. Department of Transportation has ordered the immediate inspection of 756 bridges around the country of similar design to the one that collapsed Wednesday in Minneapolis.

"Even though we don't know what caused this collapse, we want states to immediately and thoroughly examine all similar spans out of an abundance of caution," Transportation Secretary Mary Peters said in a statement. (Read More: States With Similar Bridges and States Assure Public Of Safety)