FRIDLEY — Two young sisters suffered critical burns Tuesday when two vans caught fire in a Walmart parking lot, and the owner of one of the vans was arrested.

The girls, 6 and 9, were alone in their van about 7:15 a.m. as their mother shopped. A van next to theirs caught fire, and the blaze spread to the girls’ van.

Both girls were in critical condition later Tuesday at Hennepin County Medical Center. Police Lt. Jim Mork told the Star Tribune that the 6-year-old’s burns were life-threatening.

The Anoka County Sheriff’s Office said the 70-year-old man who owned the first van was arrested and held on a negligent fire charge.

That man’s wife escaped their burning van unhurt. It wasn’t clear if the man arrested had also been in the van, and a sheriff’s lieutenant didn’t immediately respond to an email.

Witness Pamela Jacobson told the Star Tribune that she saw the flames leap from the first van to the next. She said she yelled at a woman trying to retrieve her purse from the first van.

The next thing she knew, emergency medical responders “had them laying on the ground. I don’t know how they got them out of the van. Things were happening so fast. People were running everywhere. It was craziness.”