A small group of people stood off to the side of a road near Baltimore on Tuesday afternoon, staring at a column of flames from a derailed frieght train in the distance.
"How far -- how far away you think we are?" a man asked.
Before anyone could answer, a large explosion ripped through the air, sending a response to the onlookers scurrying away: Too close.
The train explosion could be felt for miles in Rosedale, a few miles east of downtown Baltimore, where residents could see a towering black column of smoke rising into the air after the blast.
Baltimore County Public Safety officials said the train struck a large truck and that the driver was in serious condition and taken to a local hospital. They also confirmed there were two people on the CSX train at the time -- a conductor and an engineer -- but neither was seriously hurt.
Fifteen cars on the train derailed and a 20-block radius around the crash site was evacuated, officials said.
CSX officials said the train was headed from Selkirk, N.Y., to Waycross, Ga., bearing 45 cars loaded with lumber, printing paper and at least one car loaded with sodium chlorate, an explosive oxidizing agent that can also cause breathing difficulties.
A witness told the Los Angeles Times that the train slid off the tracks and was on fire before the blast, which came shortly afterward.
The effect of the blast and the moment of its detonation were captured in tweets, photos and videos uploaded to social media after the incident. Here's a link to the video that captured the blast (note: Bystanders shout obscenties).
Kevin Lindemann, 29, who was at the warehouse apparently most heavily damaged in the blast -- which came after its 15 employees evacuated -- sent The Times this video of employees' concern before the explosion.
He also tweeted this photo:
Residents and reporters around the Baltimore County area then reacted on Twitter:
Lindemann then tweeted a photo of his workplace, which he'd abandoned with coworkers just shortly before the blast.
Officials reacted to the crash:
The Washington, D.C.-based National Transportation Safety Board announced that its investigators would soon be on the scene.