With the river and the wreckage behind him, Winter told a news conference he was shocked at what he saw.
"It is something to be here and to be able to see the immensity of the tragedy," said Winter. "My thoughts and prayers go out to everyone who lost loved ones in this event, and I hope that we are able to recover all of the remains and help in the healing process."
So far, the effort to recover bodies from the water has been hampered by strong currents and low visibility. Broken chunks of the bridge are also creating dangerous conditions for divers.
Both the FBI and Navy have sent in specialized divers to help in the recovery effort.
Secretary Winter says the Navy divers are well-experienced in salvage operations. They have worked in many similar situations, including plane crash recovery salvage.
But he says the difficulty of working in the Mississippi means the effort will take more time. Winter refused to speculate on how long the recovery operation would continue, but he suggested that patience is in order.
"Managing expectations is always a challenging part of these types of activities. I think both the supervisor of diving and salvage, and also the commander in charge of the mobile diving and salvage unit on site, are comfortable with the progress that is being made," said Winter. "They've laid out a general course of events, it is structured, it covers different areas in sequence and they are working through it."
Winter says the first step is to complete the mapping of the debris field.
Rescue divers have so far pulled one car from the water that was documented as belonging to one of the people confirmed missing. But at least 11 more cars are known to still be in the water.
Minneapolis Police Capt. Mike Martin struggled to find the words to explain why it's been so difficult for the divers to pull a body from the underwater wreckage.
"As hard as it is for us to talk to people about this, and to explain it in a way that's not too gruesome -- those vehicles have been crushed, for the most part," said Martin. "There may be areas where they're protected that are inside that we haven't seen. But this is not going to be a case where they cut away rebar, and maybe cut into some of the superstructure, and then reach into a window to recover the body."
The superstructure is the framing that holds up the bridge deck. Instead, Martin says officials are trying to figure out ways to remove vehicles, so they can be taken apart off site in an attempt to recover remains.
Since vehicles lie crushed beneath the wreckage, it seems logical to begin using heavy cranes to remove the debris. But Martin says officials don't want to do that until they've exhausted all of their options.
"We're not at that point yet, and we don't want to disturb things that are on the top, things that are sitting on top, until they've explored all of the areas that they can get into," said Martin. "Because if you move something here, in an area where there's a point of entry into the bridge deck or the superstructure, it may go away or things might bend and change."
Navy and FBI dive teams are looking for ways to go deeper into the wreckage than the local dive teams who have worked since the Aug. 1 collapse, Capt. Martin said. He said he expects it to be at least a week before cranes start regularly hauling out large pieces of debris.
Debris removal had been expected to begin this week. The State Patrol said 88 vehicles have been located at the collapse site, including those in the Mississippi River.
Meanwhile, the company that was doing work on the bridge rejected a report that one of its workers had noticed unusual swaying of the bridge in the days leading up to the collapse.
Progressive Contractors Inc. had said earlier that it didn't believe any of its work contributed to the bridge failure, but hadn't responded directly to claims of wobbling.
"We have now met with every single worker who was on the bridge when it collapsed," Tom Sloan, vice president of the company's bridge division, said in a statement. "None of them observed or reported any unusual swaying."
The National Transportation Safety Board has said reports of wobbling will be part of its investigation. The agency issued a brief update of its work Wednesday, saying helicopter observations had found several "tensile fractures" in the superstructure on the north side of the bridge, but nothing that appeared to show where the collapse began.
Investigators said they have also found design issues with gusset plates -- steel plates that tie steel beams together -- but gave no other details.
At the dive site, two large cranes were ready to go. But they sat unused as Navy divers returned to the water about 7 a.m., doing "a very meticulous, hand-over-hand search of the scene," said their spokesman, Senior Chief Dave Nagle.
The FBI team had to abandon the use of the larger of their two unmanned submarines, Special Agent Paul McCabe said Wednesday.
The remote-controlled vehicle -- equipped with a camera, sonar, lights and a grabbing arm -- was too big to maneuver amid the unstable, twisted bridge wreckage and vehicles in the murky water, he said.
Instead, FBI divers will try their smaller sub, a shoe box-sized vehicle equipped only with lights and a camera. Its smaller thrusters make it more susceptible to the stiff river currents.
As the difficult and dangerous work continues at the site, law enforcement officials say they are dealing with the distraction of keeping onlookers at bay. So far they have arrested 16 people for crossing police barriers in an attempt to get up-close looks at the recovery operation.
Officials have erected tall fences around the massive perimeter of the collapse site.
Minnesota State Patrol Maj. Mike Asleson said law enforcement is adding video surveillance to the fence lines in hopes of keeping the area secure, while reducing the number of officers guarding it.
"The perimeter security well go on for an extended period. We're looking at weeks -- probably months," said Asleson. "Our role is to help provide the integrity of the perimeter until the investigators from Minneapolis and the NTSB say this is no longer a controlled death investigation scene, or an investigation of the bridge itself and why the failure occurred."
As the investigation into the collapse enters its second week, the National Transportation Safety Board is asking anyone who was involved in the disaster and who has not been formally interviewed to contact the board.
In particular, police say the NTSB is very interested in speaking with someone that witnesses saw kayaking in the area when the bridge fell down.