Associated Press

Nashua, N.H. — Police and fire officials on Monday were working to find out why an inflatable bounce house lifted off the ground and flew some 40 feet across a farm before crashing down and injuring two toddlers who were inside.

Authorities said two boys, ages 2 and 3, had climbed into the bounce house at Sullivan Farm in Nashua on Sunday when it went airborne, flying over a fence and then crashing to the ground. The younger boy suffered critical injuries and was flown to a Boston hospital. The 3-year-old boy also was injured.

Winds were blowing between 7 and 12 mph early Sunday afternoon, according to data from the National Weather Service.

The farm’s co-owner, Gary Bergeron, told WMUR-TV that the bounce house had been inflated so it could dry off and was not open at the time. But the father of one of the injured boys, who were not identified, told the station that a farm volunteer led visitors to believe it was open.

“That’s all part of the investigation,” Steven Galipeau, assistant Nashua fire chief, said Monday.

Calls to the two hospitals where the boys were taken weren’t immediately returned Monday.

Sullivan Farm is a 50-acre working farm and a popular autumn destination.

Commercial bounce houses rented for parties and other events are made of heavy vinyl, weigh 200 to 250 pounds and are secured by 18-inch steel stakes. Authorities haven’t said the size of the bounce house at Sullivan Farm.

There have been several incidents recently in which children were injured when the bounce houses they were in went airborne. In May in upstate New York, two boys, ages 5 and 6, fell 15 feet to the ground after one of the houses broke loose from its plastic anchoring stakes and was swept skyward by a gust of wind. One of the boys was put in a medically induced coma and spent more than a month in the hospital.

In Scottsdale, Arizona, a bounce house outside a McDonald’s restaurant was pushed into traffic by a gust of wind in March 2012. No injuries were reported. In June 2011, strong winds tumbled three bounce houses with children inside them at a youth soccer tournament in Oceanside, New York. Minor injuries were reported.