A 12-year-old boy who was playing Monday and became pinned under a tree in Springfield has serious injuries to his lower body, and is recovering at a local hospital, according to Fairfax County officials.

The boy and two friends were playing outside around 3:30 p.m. near Smyth Street and Barnack Drive when the boy climbed on a tree that had recently toppled, but was not completely on the ground, said Fairfax County fire department Battalion Chief Keith Ludeman.

While he was playing, the tree — which was about a foot and half in diameter — shifted, rolled and pinned him to the ground, Ludeman said.

It took rescue workers about 15 minutes to free the boy, who was then taken by helicopter to a hospital.

It was unclear when the tree initially fell, but it could have happened last week when Superstorm Sandy brought high winds and rain to the region and toppled hundreds of trees. During the storm, 52 trees fell on homes in Fairfax County.

Ludeman warned people against playing on trees or even climbing them because they are unpredictable. He said that throughout the year, the department responds at least once a month to a call for a child who has fallen out of a tree and is injured.

“People underestimate the integrity of the tree,” Ludeman said. “It’s a common thing.”

He said trees pose even more of a danger after a storm, especially if they are rotting.

“They are a lot heavier than you’d think,” he said.

Ludeman pointed to two recent events in Great Falls in which people were killed by falling trees.

A man died in July as he drove along Georgetown Pike during the evening rush hour, and a large tree next to the road fell on his car.

Authorities said the tree that killed Albert Carl Roeth III, 64, was decayed at the roots.

And last month, a man in his 50s was killed as he cut down a tree in his own back yard. He became pinned under it as it fell.