State Police say they are piecing together information to understand just how a bus carrying a Utah high school band veered off a southeastern Idaho interstate, killing a 33-year-old band teacher and injuring dozens of student musicians who hours earlier had swept a competition.

Police identified the person killed in the Saturday wreck as Heather Christensen of Spanish Fork, Utah, a woodwind instructor for the American Fork High School band. All but one of 44 students who received medical care at Portneuf Regional Medical Center in Pocatello following the accident had been released by Sunday.

Hospital officials say the remaining patient, a girl, is due to be released on Monday.

"We're trying to figure out why the bus went off the road," Capt. Eric Dayley of the Idaho State Police in Pocatello, told The Associated Press Sunday.

Debra Jarvis, 50, also of Spanish Fork, Utah, was behind the wheel of the big charter bus carrying 54 students and Christensen when it left U.S. Interstate 15 about five miles south of Pocatello.

John Miller, the band's director, was on a different bus but said he was told Christensen saw the driver slump over and leaped up to grab the wheel.

A phone call Sunday to Lake Shore Motor Coach Lines in Provo, the charter company that owns the bus that crashed, was unanswered. Jarvis remains hospitalized in stable condition. Blood and urine samples were taken, as is customary in fatal accidents. The result will likely take weeks, Dayley said.

Miller said Christensen's actions to try to steer the bus to safety seconds before she died likely kept the crash from being even worse.

"She was doing what she loved — helping kids," Miller said.

Members of the band met Sunday with Miller and his staff at the school to discuss the accident and whether they would participate in a Tuesday competition at Brigham Young University in Provo. A public memorial was to be held at the school gym after Miller and the students met.

The band, one of Utah's best-known, had just added the Pocatello competition to a string of victories that include 19 straight Utah state titles. The school band also performed at President George W. Bush's 2005 inauguration and marched in the 2007 Macy's Thanksgiving Day parade in New York.

Miller said he was getting calls and e-mails all day Sunday.

"It's just been powerful," he said. "The national band community is amazing."

The crash occurred at about 7 p.m. MDT on Interstate 15, about two miles north of McCammon and 50 miles north of the Utah border. A total of 222 students were on the trip, divided into four buses.

Idaho State Police officers said the crash scene initially was confusing and chaotic, with the other buses stopped nearby and family members steering their vehicles off the road as they came upon the scene of the tragic mishap. Distraught students sang church hymns after learning of the instructor's death.

"There were lots of young people milling about, with parents arriving," Dayley said. "We were able to come together and provide the needed medical attention and law enforcement services."

Two students were rushed by helicopter to the Portneuf Regional Medical Center in Pocatello. Another 12 students went by ambulance with serious injuries, and 30 were taken by bus with minor injuries.

"Considering everything, they're doing wonderful," Miller said. "They just had a really tough night last night."

American Fork band member James Kimball, 16, was in the bus behind the one that crashed and witnessed the wreck.

"We were watching a movie, and I looked forward and saw the bus bouncing across the side of the road," the high school junior told The Salt Lake Tribune. "The bus flew off to the side, bumped across a couple hills and rolled over."