(Bloomberg) — Two Moscow subway workers were detained in the investigation into yesterday's train crash, which killed 22 people and injured 162, the deadliest incident in the city's underground system since 2010 suicide bombings.

The workers are suspected of violating safety regulations by improperly installing the switch that failed when the train was changing tracks, causing the three lead wagons to derail and trailing cars to jack-knife, the Investigative Committee said in a statement on its website.

Nineteen people died on the scene and three more succumbed to their injuries in the hospital, according to Emergencies Ministry. More than 100 people were still being treated by midday. Rescue workers evacuated more than 1,200 people from the tunnel where the crash occurred during morning rush hour, between the Slavyansky Bulvar and Park Pobedy stations in western Moscow. The train, on the dark blue line that bisects the city, was heading away from downtown when it crashed.

The Russian capital's subway network, opened by Josef Stalin in 1935, is the world's busiest outside of Asia, carrying as many as 9 million people a day through 194 stations, according to the website of its operator, Moscow Metropolitan. The city government said last year it plans to spend $55 billion to upgrade and expand Moscow's road, rail and subway networks to boost use of public transport by 45%.

'The End'

“I thought it was the end,” one passenger said in comments shown on Rossiya 24 television, describing how the lights suddenly went out and smoke filled the carriages. Emergency workers removed some of the injured by helicopter to circumvent traffic jams.

Some of the relatives and friends of the injured who rushed to local hospitals said they were prevented by officials from learning the status of people who were hurt.

“I was told they won't give him a phone and they won't let him speak to me,” Natalya Sedykh, 23, said in televised remarks about her boyfriend, Valery.

Moscow Mayor Sergei Sobyanin visited the scene as rescue workers moved people to safety. Sobyanin, a former chief of staff to President Vladimir Putin, made improving transportation and rooting out corruption the focus of his administration after taking over in 2010 from Yury Luzhkov, who had governed the city of 11.5 million for 18 years.

Russia's ranks behind Ghana, Montenegro and Albania at 93rd out of 148 nations for the quality of its infrastructure, according to the World Economic Forum's latest Global Competitiveness Report.

A fire broke out in a subway tunnel near the Kremlin last year, prompting the evacuation of about 4,500 people and snarling downtown traffic. In 1982, eight people died when an escalator in one of Moscow's subway stations collapsed.

Security was stepped up across the subway network after 40 people were killed at two downtown stations in March 2010 by two female suicide bombers.

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