A natural childhood curiosity turned tragic for two Salt Lake County families Sunday night.

At almost exactly the same time Sunday, two children started fires with cigarette lighters in two different homes.The first, at 7:02 p.m., involved a 4-year-old who first covered her younger sister in a waterless, gel-like handsoap and then lighted her on fire, said Salt Lake County Fire Capt. Bill Brass.

The 2-year-old's chest, abdomen, thighs and arms down to her wrists suffered first-, second- and third-degree burns. The burns cover 30 percent of her body, Brass said.

When firefighters arrived, the children's father was in the parking lot holding the 2-year-old in a wet towel, he said. The child was flown to University Hospital's Burn Unit but later transferred to Primary Children's Medical Center.

County fire investigators planned to question the 4-year-old further, but she'd already admitted setting her sister on fire.

"The 4-year-old admitted she `touched (the jelly soap on her sister) with the fire and it lit,' " Brass said. "There will be an investigation . . . But children at that age are very curious about fire. It's just a sad tragedy. We're not blaming anybody."

Brass said the girls' father put the fire out. The names of the family were not released Monday morning. A spokeswoman for Primary Children's Medical Center said the 2-year-old was listed in critical but stable condition.

Fire investigators planned to refer the girl and her parents to a juvenile fire-setter program.

The second fire started shortly before 7:30 p.m. in the bottom unit of a three-story townhouse at 469 E. 2250 South. Neighbors called fire officials when they saw smoke coming from the building.

When firefighters arrived, they found the basement in flames and called in a second alarm.

South Salt Lake Police Sgt. Beau Babka said an 11-year-old boy was home alone when the fire started but escaped with a minor burn on his ankle.

The boy's parents arrived on the scene about a half hour later and took him to Cottonwood Hospital for treatment.

Babka said investigators later found a cigarette lighter and lighter fluid near where the fire originated.

"The boy told some of the medical personnel that he had been playing with (the lighter)," Babka said. "That part of it is still under investigation."

Firefighters had the fire under control by 8:15 p.m., confining the damage to the basement unit. Other apartments in the townhouse sustained some minor smoke damage and were left without electrical power.

Babka said the damage was estimated at $50,000.