An explosion in a crowd during a municipal fireworks display Tuesday injured at least 16 people, but most had been released after treatment, police said Wednesday.

The blast occurred about 75 yards from the fairgrounds display, said Sgt. Jeff McCabe of the Upper Merion police.

A single fireworks shell shot out toward the crowd instead of upward, said Lt. Tom Nolan of the Upper Merion police department.

Police had not determined Wednesday if it was an errant shot from the company handling the display or if someone else set it off, he said.

Nearly all the injured had been treated and released by Wednesday morning. The most seriously injured person suffered a hand injury, Nolan said.

The township paid $11,000 for the display by Lorusso Fireworks of Netcong Inc., a New Jersey company that has done the township's show for about a decade, Township Manager Ronald Wagenmann said.

There was no immediate response to a call seeking comment from the company Wednesday.

King of Prussia is in the Philadelphia suburbs.