Subway Derailment in Moscow Kills 20

MOSCOW — A morning commute ended in darkness, smoke and bloody mayhem for passengers on the Moscow metro on Tuesday when a train derailed underground, killing 20 people and injuring at least 100 others.

Witnesses described being suddenly heaved out of their seats and landing in piles in the center of the wagons as three cars derailed and jackknifed in a tunnel about 200 yards from the Slavic Boulevard metro stop. Passengers posted cellphone images of people walking to safety through a tunnel.

The cause was not immediately clear. The authorities blamed a power failure, a botched emergency stop or a mechanical flaw with a wheel chassis. Officials cited in Russian media quickly ruled out terrorism.