“In line with the current schedule, movement of trains will resume on Friday morning, but there may be any unpredictable aspects in the situation that may both hold and speed up our work,” Biryukov told journalists.
“We are simultaneously studying what is on tracks, what is under broken cars, so it may be either way,” he said.
The tragic accident took place at 8:39 a.m. Moscow time (4:39 UTC) on Tuesday on the stretch of the west-bound "blue" line of the Russian capital’s metro network between the Park Podedy and Slavyansky Bulvar stations.
A rapidly moving train crashed entrapping all of its passengers in the underground tunnel after three of its cars derailed due to reasons that investigators have yet to establish.
Moscow Mayor Sergei Sobyanin declared Wednesday the day of mourning in the Russian capital.