Police on Saturday were investigating the cause of an accident that killed three Alabama high school cheerleaders and injured four.

Sarah Casey, 16, Courtney Niceley, 17, and Whitney Bradford, 16, of Warrior, Ala., died when the car they were in struck a tree and went over an embankment, according to Dorris Teague, a spokeswoman for the Alabama Department of Public Safety.

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The driver, Sarah Elizabeth Agee, 17, as well as Brittany Lovejoy, 17, Ariel Nibblet, 17, and Alexandria Thomas, 16, were injured, Teague said.

The Blount County coroner, John Mark Vaughn, said the girls were laughing, singing and "cutting up" moments before the driver lost control on a straight stretch of road.

"It looks like she was just distracted. If you can imagine a bunch of kids in a car like that, it's not hard to understand," he said.

All the teens attended Hayden High School and were on their way home from a cheerleading clinic at the time of the crash, authorities said.

"I'm going to remember their smiles and their school spirit," said Allen Hargett, the school's principal. "They were happy girls and they loved being here, and people loved being around them."

A Web site for the high school's athletics department expressed condolences to the families of the deceased Friday morning.

"They will forever be in our hearts!" it read.

The accident occurred on Alabama Highway 160 about 10 miles east of Hayden, Teague said.

The 2006 Chevrolet Malibu was traveling westbound at around 9:10 p.m. Thursday when it struck the tree and went over the embankment, Teague said.

Some reports said the driver had run off the highway and over-corrected, but Teague declined to discuss details of the one-vehicle crash pending the outcome of the ongoing investigation.

FOXNews.com's Sara Bonisteel and The Associated Press contributed to this report.