FRIDLEY — Two young sisters were burned, one critically, when a van caught fire in a Walmart parking in a northern Minneapolis suburb.

Authorities say the girls were alone in the van Tuesday morning for 45 minutes to an hour as their mother shopped in the store in Fridley. A van next to the girls’ van caught fire around 7:15 a.m., and the blaze spread to the girls’ van.

Fridley police Lt. Jim Mork says a 6-year-old girl suffered critical burns. Her 9-year-old sister suffered less serious burns. The Star Tribune reports both were taken by ambulance to HCMC.

Mork says the girls’ mother was “hysterical.” He says the fire is not considered suspicious. A woman sitting in the first van that burned escaped without injury.