Washington, DC – Eight people were transported to a hospital after a carbon monoxide leak on a ship participating in D.C.’s annual holiday boat parade on Saturday evening.

Around 7 p.m. Saturday, D.C. Fire and EMS officials received a call over marine radio from a private vessel in the Washington Channel reporting that one person on board had fallen unconscious and others were feeling ill.

Harbor units were immediately dispatched, the department tweeted. Sixteen people were evaluated for carbon monoxide exposure, with eight — including three children — requiring transport to a hospital in a non-life threatening condition.

Eight others were evaluated and release at the scene.

The vessel was towed to shore for further investigation and firefighters are currently investigating the cause of the leak.

As an annual D.C. tradition, the boat parade sees dozens of colorfully-lit ships pass The Wharf in Southwest D.C. with a fireworks salute and live music.