A tractor-trailer truck crossed the median of an Arizona highway Sunday and slammed into a van driving in the other direction, killing all seven of the van's passengers, a state public safety spokesman said.

The two people in the truck -- the driver and his spouse -- were both injured in the crash and helicoptered to Banner Good Samaritan Hospital in Phoenix, said Officer Carrick R. Cook with the Arizona Department of Public Safety.

The spouse has a broken back, and she and her husband are both in serious condition, according to the spokesman.

The truck had been heading west on Interstate 10, about 40 miles west of Phoenix, around 11 a.m. (2 p.m. ET) when it went across the highway and struck the van driving east.

Both vehicles went off the right side of the highway after the collision and caught on fire, said Cook.

Medical examiners are trying to determine the identities of the seven van passengers killed, she added. They are believed to be from western Arizona.

The crash caused massive traffic issues, as authorities shut down Interstate 10 eastbound before noon and funneled drivers off the highway. One lane was reopened around 4:30 p.m., according to the state Department of Transportation's official Twitter feed.