During rush hour on Tuesday morning, a crowded subway train went off the rails in Moscow.
More than 24 hours later, Russian authorities say at least 21 people are dead and more than a hundred are injured.
The death toll is expected to rise as dozens among the hospitalized are in critical condition.
The crash took place around 8:35 a.m. local time, when three cars on the train, which was traveling at 70 kilometers per hour, braked suddenly between two stations in the west of the capital city.
"I was in the very front carriage and it was a great shock. The lights went out and people fell to the ground."
"The train stopped abruptly and the passengers fell to one side. There was smoke and we were trapped inside."
The exact cause of the crash has not yet been determined, but emergency officials blame a power surge that scrambled the metro's electronic control systems.
"We are investigating all possible causes of the crash, except for one which we've ruled out - a terrorist attack."
Moscow's mayor has declared a day of mourning for the dead.
The capital's subway system is used by some 11 million people every day, and despite being one of the world's oldest underground railways, fatal accidents like this one are rare.
Kim Min-ji, Arirang News.