MINNEAPOLIS - A Minnesota bus company remains confident that a driver's sudden medical emergency led to the fatal tour bus crash earlier this week that killed two and injured 20.

The attorney for Strain Tours, John W. Patton Jr., said Friday it's also clear to him that there were no maintenance issues with the bus.

Company officials say the driver, 52-year-old Ed Erickson, suffered a ruptured aneurysm just before the crash Wednesday. Patton said Erickson remains in intensive care at Mayo Clinic.

The two most seriously injured passengers are listed in serious condition at the Mayo hospital in Rochester, an improvement from critical condition Thursday night.

The accident happened near Austin. State investigators have said determining the cause could take weeks.