Authorities were trying Friday to identify the most recently discovered human remains from last week's interstate bridge collapse in Minnesota as recovery teams worked to find more bodies of the handful of people still missing.

Two days after joining the search, U.S. Navy divers recovered the remains of two, or perhaps three, people from piles of debris from the Aug. 1 collapse of the Interstate 35W bridge.

Authorities identified Peter Joseph Hausmann, 47, from nearby Rosemount, as one of those whose remains were recovered. Divers later found more remains initially thought to have belonged to one person, but authorities later said they may have belonged to two others. They were not immediately identified.

"The additional remains appear to probably represent more than one individual," said Medical Examiner Andrew Baker.

Hausmann was among eight people listed as missing and presumed killed. Among the others were a pregnant nursing student and her 2-year-old daughter, and another woman and her adult son, who has Down syndrome.

At least eight survivors remain hospitalized. The one remaining victim who had been in critical condition at Hennepin County Medical Center was upgraded to serious condition Friday, a hospital spokeswoman said.

Hennepin County Sheriff Rich Stanek said the dive team had been able to penetrate most of what is called the debris field, the area where the bridge's deck collapsed. There are a few of those spots left to penetrate, after which "some debris may have to be removed significantly before we make additional recoveries," Stanek said.

Baker said it might become more difficult to positively identify remains now that they have been in the water more than a week. He said dental records and DNA evidence would be used if needed.

Hausmann was a computer security specialist and a former missionary who met his wife, Helen, in Kenya. The evening of the collapse, he was heading to St. Louis Park to pick up a friend for dinner. Hausmann called home while sitting in traffic, but the line went dead.

As searchers combed the river, federal officials issued a national advisory for states to inspect the metal plates, called gussets, that hold bridge girders together.

Investigators said the gussets on the failed Minneapolis bridge were originally attached with rivets, old technology that is more likely to slip than the bolts used in bridges today. Some of the gussets also might have been weakened by welding work over the years and some of them may have been too thin, engineering experts said Thursday.

Questions about the gussets prompted Transportation Secretary Mary Peters to caution states about stress placed on bridges during construction projects.

Investigators are also looking at whether extra weight from construction work could have affected the bridge. An 18-person crew, heavy equipment, and piles of sand and gravel had been on the span when it collapsed during the evening rush hour.

Bruce Magladry, director of the National Transportation Safety Board's Office of Highway Safety, said the agency will use a computer to simulate how the bridge might have behaved with different loads, and with different parts of the bridge failing.

Observations from a helicopter camera this week found several "tensile fractures" in the superstructure on the north side of the bridge, but nothing that appeared to show where the collapse began, the NTSB said.

Also on Thursday, President George W. Bush dismissed a proposal to raise the federal gasoline tax to repair America's bridges at least until the U.S. Congress changes the way it spends highway money and considers the economic impact of a tax increase.