The deadly derailment in the Moscow metro was preceded by the construction of a new track, the metro chief said Wednesday.
"Yes, certain works took place there related to building a second track to the Delovoy Tsentr station," Moscow metro chief Ivan Besedin said, when asked whether any kind of construction was carried out in the vicinity prior to the accident.
Besedin added that the tracks of the Arbatsko-Pokrovskaya line, where the crash took place, were "in good condition."
The accident occurred on Tuesday during the morning rush hour in the tunnel between the Molodezhnaya and Slavyansky Bulvar stations on the dark blue Arbatsko-Pokrovskaya line as three cars of a train derailed inside a tunnel.
The Russian Health Ministry said a total of 161 people have been injured. Over 120 of them have been hospitalized. Helicopters delivered 24 victims who were critically injured to hospitals.
Avtandil Mamvelidze, the deputy chief of Moscow's Hospital Number 31, said on Wednesday that another "patient in extremely grave condition died today," bringing the total death count to 23. A medical source told RIA Novosti on Tuesday evening that the 22nd victim had succumbed to his injuries. The Emergencies Ministry confirmed the information early on Wednesday.
Earlier the same day, the Russian Investigative Committee detained rail engineer Valery Bashkatov and his aide, Yury Gordov, over the deadly accident. According to one of the versions, the train may have derailed due to the incorrect installation of a cable that snapped in a rail junction switch.
No evidence has so far been found to substantiate the initial version, which said that the train stopped abruptly when a sudden short-term power outage triggered the emergency brakes.
Russian President Vladimir Putin expressed his condolences to the families and friends of the victims and wished a speedy recovery to the injured.