SAND SPRINGS, Oklahoma - The fire at the Pier 51 Marina on Keystone Lake was still smoldering Monday morning. Flames destroyed eight boats overnight.

Firefighters moved still-burning boats from the dock, put a boom on the water to prevent fluids from spreading, and let them sink.

Representatives from several agencies have arrived on scene to help with the investigation.

Crews were called out to the marina around 9:30 p.m. Sunday. Several boats were engulfed and people trapped on the other side of the dock when firefighters arrived.

The Keystone Fire Chief Chris Blackburn confirms no one was hurt at the D dock where the fire started, and those who were trapped on the other side of the dock either drove their own boat to safety or were rescued by first responders.

Keystone told us it may have started on a houseboat and spread from there, but the fire marshal is now investigating the official cause. Keystone Fire counted at least seven boats that were lost, but they don't know how many sank.

So, the fire chief says, getting a final count could take up to a couple days.

It was a very unique and challenging fire to fight. The walkway boards leading to the dock were burned up, but despite the bad footing, no firefighters fell into the water.

Blackburn said it was their first dock fire - before now, they'd only put out individual boat fires.