LARIMER COUNTY, Colo. (CBS4) – Poudre Fire Authority firefighters responded to Horsetooth Reservoir Saturday morning after they say a boat exploded. Six people were injured.

The explosion, and fire above the water, grew so hot it sent them into the water.

(credit: Gustavo Smithy/Twitter)

One person was taken to the hospital by helicopter, three were taken by ambulance and the remaining two were treated at the scene, fire officials say.

(credit: Erika Gelwicks)

Smoke could be seen coming from the Inlet Bay Marina. Firefighters said, upon preliminary investigation, the explosion may have followed trouble with a faulty engine. They say the boat had an outboard motor.

“Witnesses reported a boat had just left the marina and they had difficulty getting the boat started,” said Chris Wolf, a spokesman for Poudre Fire Authority. “They started the motor and it exploded.”

“I’ve been up here for 36 years and never seen anything like it,” said Jeanie Wiesman, a witness.

Wiesman was one of many who were hiking around the lake when they heard and saw the explosion.

(credit: Jeanie Wiesman)

She said she watched as victims tried to make their way toward shore.

“I saw victims being pulled out and then flight for life taking them off,” Wiesman said.

(credit: CBS)

Firefighters controlled the fire at around 10:20 a.m. The boat was then removed from the reservoir.

(credit: Poudre Fire Authority)

It is unclear what caused the explosion. Investigators say they could release more information on Monday.

Danielle Chavira