(CNN) -- Two young boys from upstate New York were recovering Wednesday after falling nearly two stories when a gust of wind swept up the inflatable bounce house they were playing in, police said.
The boys, ages 5 and 6, were seriously injured Monday while playing in a yard near their apartment building in South Glens Falls, New York, police said. The bounce house was swept up in a "sudden and strong burst of wind," according to a police statement.
The boys fell to the ground after the inflatable house was lifted 15 to 20 feet into the air, police said.
The 6-year-old was found in the street, and the 5-year-old was found in the apartment building parking lot, police said. The boys were airlifted to Albany Medical Center, but the extent of their injuries was not known.
A police investigation determined that several adults were monitoring the children and that the bounce house had been properly staked to the ground.
Stephanie Hansen, who lives in the apartment building, had seen the house being set up earlier Monday. She called 911 after being told about the accident.
"It was nothing that anyone did wrong," she said. "I saw the house being put up. I saw him putting all the stakes in. The parent, he just broke down. It was the saddest thing, he was blaming himself. He did everything right, it was just a freak thing."
The families of the injured boys could not be reached for comment.
Hansen told CNN that a third child, a 10-year-old girl, was also injured but not seriously. She was treated at the scene and not immediately taken to a hospital.
Little Tikes, the bounce house manufacturer, said it was investigating the incident.
"Providing safe and wholesome play experiences is of utmost importance to Little Tikes," the company said in a statement. "We are looking into what happened in South Glen Falls. ... In the meantime, our thoughts and prayers are with the children and their families."
No charges have been filed. Although an investigation was continuing, police said they considered it a "tragic accident."
South Glens Falls in a small village about 55 miles north of Albany.
Bounce house-related injuries have been increasing in the United States. A study by Dr. Gary Smith of the Columbus, Ohio-based Nationwide Children's Hospital found that the number of related injuries rose 1,500% between 1995 and 2010.
From 2008 to 2010, the rate of injuries more than doubled, according to the study, which was published in the journal Pediatrics in 2012.
In 2010 alone, 31 children were treated in emergency departments each day on average, according to the report. "That's about one child every 45 minutes," Smith, who is the director of the Center for Injury Research and Policy at Nationwide Children's Hospital, said at the time.
Smith said the pattern of injuries from inflatable bounce houses is similar to injuries suffered from trampoline use. But while there are national safety guidelines for trampolines, there are none for inflatable bounce houses.
CNN's Miriam Falco contributed to this report.