MINERAL SPRINGS, NC (WBTV) - It could be weeks before we know how a deadly train collision happened in western Union county Tuesday morning.
Two CSX crew members died in the fiery crash. Two others were injured Tuesday when a speeding train slammed into another in the middle of the night in the town of Mineral Springs.
So, how does something like this happen? How do trains collide?
A train ramming into another is extremely rare, however it does happen.
CSX officials are saying they don't know if the cause was mechanical or human error but train experts we talked to today lean toward operator error.
Don't think these things are powerful? Pictures circulate the internet of a speeding train that was knocked off its tracks by a tornado.
It kept on blowing down the line. Train experts say a fully loaded freight train can take up to a mile to stop.
What happened here in Mineral Springs just before four o'clock Tuesday morning - the train didn't stop.
"It's very unusual. It really is."
Gus Ubaldi is with the firm Robson Forensic - one of the country's leading railroad experts. He outlined three scenario that could have taken place to cause this crash and where investigators will be focusing their efforts over the next week.
He's inclined to believe it was most likely operator error. Either by engineer and conductor in the first train. The team in the second train. Or by a railroad dispatcher.
The first train was stopped.
If it was a break down, they could be at fault for failing to walk back half-mile down the line and setting flares letting oncoming trains know they're broken down.
Train Number 2 could be at fault for failure to heed signal markers - stopping up the line where they were supposed to stop.
And the third possible scenario - failure by the dispatcher - giving train number 2 the go ahead when he wasn't supposed to.
"Those kind of scenarios would be human error," says Ubaldi.
The technology of trains hasn't changed much in the last 150 years. It's still basically a steel wheel on a steel rail. And it works very well, most of the time.
There are thousands of trains on tens of thousands of miles of track hauling tens of millions of tons of material each year.
But accidents happen and when they do they get our attention.
Neighbors like Allen Greer who live along tracks see something like this and alarms go off in their head.
"You just have to pray about it cause you never know.. you're so close to the tracks. I hear it all day long. I'm very concerned," says Greer.
The National Transportation Safety Board has three investigators looking into this crash. They will be aided by three inspectors from the Federal Railroad Administration which oversees train safety.
They'll be interviewing train personnel and witnesses, inspecting the equipment, tracks and seeing if there are tapes available and pouring over the railroad's records.
How long will it take?
NTSB told us they're on scene - in the area 3-to-7 days. They told us it's a process of elimination. They look at everything and then narrow it down.
A report will take about a year to put together.
The NTSB doesn't investigate every train crash, only about a dozen a year. This one rose to the level of being investigated because it involved fatalities. The train engineer and conductor of the train that didn't stop were killed.