Killed was the driver, 53-year-old Susan Clark, and her husband and front-seat passenger, Steven Clark, 55, of Provo. They were dead at the scene, UHP said.
Suffering minor injuries were eight passengers ranging in age from 3 to 23. Seven were family members.
According to The Spectrum, UHP troopers said the passengers were the Clarks' adult son and two adult daughters; a daughter-in-law and her twin sister; two grandchildren; and a Chinese foreign exchange student.
They were transported to Dixie Regional Medical Center in St. George, UHP said.
Friends and neighbors remembered the Clarks as a humble, cheerful and hard-working couple.
"[Susan Clark] always laughed a lot," said Annalee Wright, one of the Clarks' neighbors. She remembered when the Clarks' house in Canada had a water leak that caused considerable damage, but Susan Clark managed to find humor in having to drive back and forth between Canada and Utah.
Wright said the Clarks were also service-oriented and sent cookies to her home when she was hospitalized.
Friday afternoon, the Young Women's group from the Clarks' Mormon ward were at the family's house, cleaning it in anticipation of their return.
Susan Clark served as the Young Women's president, said Camille Troutner, who was her first counselor.
"Both of them were so humble and so loving," Troutner said. "They always thought of other people."
Randy Robertson, another neighbor and friend, said the Clarks were driven people and that Steven Clark's business was taking off. He was the American distributor for a German pipemaker whose parts are used in radiant-heat systems.
"They truly were the nicest people I have ever met," said neighbor Brandon Chambers.
No one living in the town houses was injured.
American Fork resident Mark Gallup told The Spectrum that he was visiting his sister in one of the town houses when the crash occurred.
"I was sleeping about 10 to 15 feet from where that thing came to rest," Gallup told the newspaper. "I heard what I thought were two loud explosions. Obviously that was when it went through the retaining wall. And then I heard a hissing sound. ... Oh my gosh, you ought to see the destruction."