Sixteen people were injured in a boat explosion at a marina in the Lake of the Ozarks in Missouri, authorities said.

The explosion, which took place at the Millstone Marina, was set off by a spark and gas fumes that "built up in the engine area," the Missouri State Highway Patrol said in an online post on Friday.

Photos posted online by authorities showed shattered glass on the boat and damage that appears to have been caused by the explosion.

Most of those injured were on the boat, authorities said.

In an incident information report, the highway patrol said the vessel was fueling at the marina's gas docks, and when its operator started the boat, it caused "an explosion in the engine compartment."

At least three passengers were ejected from the boat, the report said.

The injuries range from minor to moderate, the highway patrol said in its post.

Eleven people, including a 6-year-old girl, were treated on the scene and released, according to the report, while five others were taken to a hospital.

An investigation into the incident is ongoing.

Lake of the Ozarks, a popular summer vacation spot in the Midwest, boasts more than 1,100 miles of shoreline.