Crews in boats were using sonar to search the water, said Hennepin County Sheriff Rick Stanek. The bridge is too unstable to allow divers into the water, he said.
As the sun rose this morning at least two patrol boats were visible on the river south and east of the lock and dam and just uptream from the collapsed bridge.
Many rescuers who'd been at scene as late as 2 a.m. were expected back at 6 a.m. for an operations briefing. Then, they were going to go back onto the water.
An hour before sunrise, nearly a dozen giant lights mounted on the Cedar Avenue and surviving parts of I-35W bridge illuminated river surface.
The 1,907-foot bridge fell into the Mississippi River and onto roadways below. The span was packed with rush hour traffic, and dozens of vehicles fell with the bridge leaving scores of dazed commuters scrambling for their lives.
Stanek told the Associated Press at about 1 a.m. today that all search efforts had been called off for the night and that searchers did not expect to find any survivors.
Wednesday night, Gov. Tim Pawlenty said the bridge collapse "is a catastrophe of historic proportions for Minnesota."
Between 50 and 60 vehicles were on the bridge when it went down shortly after 6 p.m., authorities said. Legions of rescue workers and volunteers swarmed to the scene and spent hours sifting through the wreckage in a frantic search for survivors.
By late in the evening, officials said efforts at the Mississippi had switched from rescue to recovery.
Jay Danz, 45, of St. Paul, was on his way to the Metrodome to watch the Twins play Kansas City and had driven under W. River Parkway, beneath the interstate bridge, seconds before it fell.
"I heard it creaking and making all sorts of noises it shouldn't make," Danz said. "And then the bridge just started to fall apart."
In addition to the cars that went into the water, a school bus carrying about 60 Minneapolis children fell from the bridge, landing on all four of its tires and missing the water as it came to rest near the parkway.
Several of the children and at least two adults were treated for injuries after the group escaped through the back door of the bus.
"Some kids had blood on their faces, but thank God everybody could move," Danz said.
Bernie Toivonen of Minneapolis was southbound on I-35 Wednesday when he saw the bridge in front of him buckle.
"I knew it was going down," he said.
Toivonen scrambled out of his vehicle, and helped others who were stranded among the wreckage.
"I helped a lady get out of a minivan. She was at a real steep angle. There were people screaming."