A toddler was flown to a Boston hospital Saturday night after falling into a fire pit during a birthday party in Billerica, police said.

The girl, who is 2 ½ years old, was with her parents at the backyard party at 101 Bridle Road when she “slipped and fell into the fire pit’’ around 6 p.m., Billerica police Deputy Chief Roy Frost said.

The girl was burned on her legs and the side of her body, Frost said. She was quickly placed in water to “mitigate any burn injuries,’’ according to a statement by the department.

Frost said the girl was airlifted to a Boston hospital for treatment and was in stable condition Saturday night.

Fire investigators at the scene concluded the incident was an accident, Frost said, adding that the adults at the home were not drinking. He said he does not expect any criminal charges to be filed.

Fire officials also determined the fire pit was well-managed, Frost said.

“It was a very safe fire pit,’’ he said. “[Officials] felt it was one of the safer ones they’ve seen.’’

Frost noted, however, that accidents can happen, even around safely contained fire pits. He recommended that ­homeowners be cautious about potential tripping hazards around open fires, particularly when children are present.

“You have to have a lot of supervision around these things,’’ Frost said. “You just have to be very vigilant.’’

Felicia Gans can be reached at felicia.gans@globe.com. Follow her on Twitter @FeliciaGans.