DENVER -- An antique train derailed on a track crossing a busy downtown Denver street, causing a blocks-long traffic jam amid the Democratic National Convention.

The derailment was near 15th & Wewatta Street in downtown Denver.

Engineer Harry Krening said no one was injured. He said the car derailed because debris from a nearby construction project got on the tracks.

The car was coupled to one of the railroad's historic steam engines when it derailed this afternoon. The engine stayed on the tracks, so crews disconnected it from the car and moved it away, clearing two of the four lanes.

The derailed car is blocking the other two lanes.

Thousands of people are visiting the Mile High City this week for the convention, and the derailment is making already-jammed streets more congested.