ORLAND, Calif. (AP) — It was a busload of opportunity: young, low-income, motivated students, destined to become the first in their families to go to college, journeying from the concrete sprawl of Los Angeles to a remote redwood campus 650 miles north.

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Those dreams shattered for some Thursday in an explosive freeway collision that left 10 dead — students, chaperones and both drivers — and dozens hospitalized.

Desperate families awaited word about loved ones Friday, while investigators tried to figure out why a southbound FedEx big rig swerved across the grassy divide of California's key artery before sideswiping a car and slamming into the tour bus, which burst into a furious blaze.

The Serrato family, whose identical twin 17-year-old daughters set off on the adventure on separate buses Thursday, had a panicked, sleepless night. Marisol made it to their destination, Humboldt State University, but the family had no word on Marisa, who had been aboard the now-gutted bus, for nearly 24 hours.

They received the official word Friday evening when dental records confirmed Marisa was among the dead.

"Marisol is devastated," the girls' 23-year-old brother Miguel Serrato said.

Humboldt alumni Michael Myvett, 29, and his fiancee, Mattison Haywood, who were chaperoning, also were killed. Myvett was a therapist at an autism treatment center.

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High school students, Jazmine Villalobos, 14, left, and Michelle Lopez, 14, react after learning the … "He just died," his grandmother Debra Loyd said, her voice breaking with emotion in the early afternoon Friday. "They have already confirmed it."

Myvett's manager Kyle Farris said he was "extraordinary," and that he connected with their children "on a level few others could, and he contributed to their wellbeing in such a positive and profound way."

"He will be greatly missed," Farris said.

A Facebook photo shows Haywood flashing a shining diamond engagement ring on her finger and kissing Myvett in December near the Louvre Museum in Paris.

The bus was among three Humboldt had chartered as part of its two-day Preview Plus program to bring prospective students to tour the Arcata campus, according to university officials. Before launching the event Friday, university Vice President Peg Blake's voice broke as she asked a crowded theater for a moment of silence in honor of everyone affected by the accident.

The CHP and the National Transportation Safety Board were investigating, but warned it could take months to conclude what happened.

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Map locates Orland, Calif., where three vehicles crashed and killed at least nine; 6c x 2 inches; 29 … Mark Rosekind, an NTSB member, said Friday that the agency would be gathering information over the next one to two weeks. He said it will review whether the stretch of California freeway where the bus was struck should have had a barrier along the median to prevent head-on collisions.

In addition, Rosekind said it will determine whether a fire suppression system recommended but not mandated for buses would have made a difference in the crash.

Most survivors were injured, some with critical burns or broken limbs. Those who made it out said they scrambled through a kicked-out window. One man, apparently an