Investigators on Thursday were interviewing passengers and examining a tour bus as they continued to look for the cause in the bus crash that left two people dead and 21 injured in southern Minnesota.
Investigators said they could not confirm the bus company's claim that the driver, Edwin Erickson, 52, of Elgin, suffered a ruptured aneurysm in his chest that might have caused the accident Wednesday afternoon.
"We haven't heard that from any medical professionals," said Capt. Matt Langer of the Minnesota State Patrol.
Langer told reporters in St. Paul today that determining the cause of the crash could take months.
"Rather than rely on a third-hand account from the owner of the bus company involved in this crash, the State Patrol would much prefer to hear those accounts directly from medical professionals," Langer said. "There's a great deal of testing, other things to go on with that driver, before we can definitively hang our hat on any cause -- whether it's medical, equipment or anything else related to the bus."
An employee with Strain Bus Line Motor Coach Tours of Rochester told MPR News that Erickson suffered the aneurysm. The employee, Cassie, who declined to give her last name, said the bus company has hired an attorney who will be flying to Rochester later Thursday.
"He lost consciousness and he blacked out," Cassie said of Erickson, adding that bus company owner Dalmer Strain had visited Erickson Wednesday night. She said Erickson was in stable condition Thursday morning at St. Marys Hospital in Rochester.
The State Patrol on Thursday identified the two passengers who were killed as Rhonda Hill, 52, of Plainview, and Pamela Holmquist, 56, of Kasson.
Eleven passengers remained hospitalized a day after the crash. Most of them were in fair condition at Austin Medical Center and Albert Lea Medical Center. One passenger was in serious condition in Rochester.
All three hospitals are run by Mayo Health System, which planned to have updated conditions later Thursday.
Conditions on Interstate 90 near Austin were clear on Wednesday when the bus crossed the median into the westbound lanes and landed on its side in the ditch. It was on its way back from Diamond Jo Casino in Northwood, Iowa, and most of the passengers were senior citizens.
Erickson started his shift on Wednesday at 8:15 a.m. in Rochester, before driving about two hours to the casino. Cassie, the bus company employee, said Erickson stayed in Northwood for four hours without driving, while the bus passengers were inside the casino.
The route Wednesday went through Byron, Kasson and Dodge Center, she said. Erickson should have been back in Rochester by 4:30 p.m. or 5 p.m.
Erickson is the company's only full-time driver, operating the tour bus three to four times a week. His last shift had been Monday and he wasn't scheduled to drive again until next week.
Erickson has worked for the bus company since 1996.
Langer, the State Patrol spokesman, said Erickson had a valid commercial driver's license, but he declined to comment on Erickson's medical records, which bus drivers are required to carry and keep up to date.
Langer said investigators are looking at a variety of things that could have played a role in the crash, and that Erickson's medical condition was just one piece of the investigation.
"Investigations like this take a great deal of time," Langer said during the news conference.
Getting information about Erickson's medical condition isn't always easy, Langer said. Authorities must get the patient's permission to get any information, otherwise they would have to ask a judge for a search warrant.
Passenger Ardell Swenson, 71, of Austin, said she was just putting her head back to rest when the bus crashed.
"When I got myself organized there was all kinds of red and white and blue lights flashing," Swenson said. "There was glass all over."
The bus was taken to Midtown Towing in Austin Wednesday night. Its front end and roof were badly damaged and most of the windows were gone, but its tires appeared to be fully inflated.
On Thursday, commercial vehicle experts were examining the bus to see if there were any equipment failures.
Strain Tours, which is also known as Bold Lines Inc., is a small operator with six drivers and four buses and has had no accidents in the past two years, according to the Federal Motor Carrier Safety Administration Web site.
In 2002, Bold Lines paid $20,000 to settle an enforcement case over drug testing for drivers, according to the federal safety agency. It also paid $300 to settle a case over driver duty times and record keeping.
The agency has advised roadside inspectors to inspect the company's vehicles because of safety concerns, according to the Web site. Its "Inspection Selection System" rated Strain at a 76, with any score between 75 and 100 meaning an inspection is warranted.
The crash happened two days after the U.S. Secretary of Transportation announced that the federal government is considering a requirement that all coach buses have seat belts and extra safety features for bus roofs. The proposed changes are in response to two accidents since 2007 in which passengers were killed when they were thrown from the bus.
Langer said it was too early to tell if that would have made a difference in the crash.
(The Associated Press contributed to this report.)