Firefighters used ladders to evacuate dozens of passengers from the "Blue Train," one of two trains in the monorail system.
About 40 people were evaluated at the scene for respiratory problems from the smoke, Seattle Fire Department spokeswoman Helen Fitzgerald said.
Nine people, including a firefighter who injured a knee, were taken to Harborview Medical Center, but none of the injuries was considered serious, and none appeared to be burns, she said.
Witnesses reported a metallic grinding for about 3-5 seconds as the train exited the tunnel through the EMP and then a loud explosion. They said smoke then started pouring out from beneath the train. People on board the train started moving to the front of the train and that's when the flames broke out.
People tried to get close to the ground and away from the flames. A short time later, monorail officials pulled up the second monorail train so people could evacuate to the red train. But one witness says the wind was blowing the smoke into the red train, so they abandoned that idea.
The fire department arrived a short time later and brought the fire under control. They then began evacuating passengers from the red and blue trains via ladder trucks.
Fire officials said the fire was brought under control Monday evening. Streets were closed in the area.
About 150 people were on the train at the time of the fire. Fitzgerald says the cause was caused by a short in the electrical wiring to the motor.
The fire occurred as thousands of people gathered at the Seattle Center for the annual Folklife Festival on the holiday weekend.
The Experience Music Project is a rock 'n' roll museum known for its unusual design as well as its collection of music artifacts.
The monorail, which includes both the "Blue Train" and a "Red Train," runs through the museum on its pathway between the Seattle Center and downtown Seattle.
Video from our photographers shows extensive damage to the blue monorail, with part of the floor and roof melted at part of one section.
Both trains will be out of service for an undetermined amount of time.
The monorail was originally built for the 1962 World's Fair in Seattle.
There have been several incidents over the years when the fire department's high-angle rescue team has been called out to remove passengers when a train broke down.