Burning diesel fuel pools hydrogen quickly rises.
https://www.nbcwashington.com/news/local/metrobus-flames-plume-smoke-dc/4095269/
Metrobus catches fire under National Mall. Hybrid diesel fleet pulled
The hybrid diesel bus was engulfed in flames, sending smoke over the city.
By Joseph Olmo and NBC Washington Staff Published April 23, 2026 Updated on April 24, 2026 at 11:12 pm
https://www.nbcwashington.com/video/news/local/9th-street-tunnel-metrobus-fire/4095683/
A Metrobus caught fire in the 9th Street tunnel under the National Mall Thursday evening and sent a huge plume of smoke over downtown D.C. Metro pulled its fleet of hybrid diesel buses.
The fire engulfed the bus. Metro is taking all 32 of its hybrid diesel buses out of service as a precaution while they investigate.
The 9th Street tunnel at 9th Street and Constitution Avenue NW were closed to traffic gor almost 24 hours before two southbound lanes reopened Friday evening.
We are a very safe system; we know that we are, General Manager and CEO Randy Clarke said. With that said, its happened. We want to work with our partners. Well do forensic investigations. We will learn from investigations. And we get better.
https://www.nbcwashington.com/video/news/local/metro-hybrid-diesel-bus-fleet-metrobus-fire/4095353/