The fire erupted around 2:30 a.m. at a marina in the area of Northwest 22nd Avenue and 14th Street.
Video taken by firefighters shows two yachts on fire near the 22nd Avenue bridge.
One yacht was about 70 feet long and the other was about 50 feet long.
City of Miami Fire Rescue Lt. Pete Sanchez said 17 units responded to the scene, fighting the blaze from both the bridge and from a fireboat.
“The conditions were intense,” he said. “That’s why we had multiple units from the bridge, from the water and land. We’re also dealing with a lot of fuel, a lot of plastics, so we also had to use a foam operation. That’s why our hazardous materials team was here.”
Sanchez said the flames were about 70-feet-high when firefighters arrived.
It took crews about an hour to extinguish the blaze.
The cause of the fire is unclear at this point, but authorities said it appears that no one was onboard either boat at the time.