FORT PIERRE, S.D. (KELO) — The mother of two boys hurt in a home explosion southeast of Fort Pierre says her sons are in stable condition at a burn center in St. Paul.

On their CaringBridge page, Kelsey Hupp says doctors updated three-year-old Royce’s burns to being on 36% of his body. She says doctors are optimistic that he could heal on his own without grafts.

Hupp says five-year-old Myles’ burns are all superficial. She says doctors will slowly wean down his sedation and do some trial breathing off the ventilator.

The house explosion on Wednesday killed 6-month-old Harper as well as the kids’ grandparents LaDonna and William Hupp.

The cause of the explosion is still under investigation.

So far, a GoFundMe for the family has raised more than $400,000.

There is also a fund set up at First Dakota National Bank.