(CNN) Nine people were injured in Pennsylvania Sunday after lightning struck a tree causing it to fall on a tent, said Bill Oettinger, the emergency management coordinator for Lower Southampton Township.

The tree fell at the Dolphin Swim Club, an open park in Bucks County about 20 miles northeast of Philadelphia, shortly after 5 p.m. ET, Oettinger told CNN. Oettinger said he knew the tree had been struck by lightning because of the burn marks.

Two adults and seven children were injured, CNN affiliate WPVI-TV , citing authorities, reported.

"The lifeguard and staff that were here got everybody out from the tent before the first responders got here," Oettinger told WPVI

Three people were seriously injured, while six others suffered minor injuries, he said.