Schroder said staff shut down the ride and evacuated visitors from the surrounding area. He said "our guests were on the ride," but that he did not know whether any passengers were carried under the roof when it was on fire.
"That type of material puts out a lot of black smoke," Orlando Deputy Fire Chief Greg Hoggatt told the Orlando Sentinel.
About 40 firefighters responded to the fire, which was brought under control in about a half-hour. Hoggatt told the newspaper that investigators were looking into whether an electrical problem triggered the blaze.
The fire department referred phone calls late Saturday to Universal Orlando.
It was unclear how many people had to be evacuated. Schroder said the Orlando fire department assisted a small number of visitors who said they had inhaled smoke.
The ride remains shut down while the blaze is under investigation. Schroder said he did not have a damage estimate or know when the ride would reopen.
"We're still reviewing that. Too soon (to say) tonight," he said late Saturday.
But he said the area known as Toon Lagoon, which includes the log float ride, reopened Saturday evening. The theme park itself also remains open.