A track supervisor and his assistant have been arrested in connection with a train accident Tuesday on Moscow's metro line that killed more than 20 people, BBC reported.

The two metro workers are thought to have used improper wiring in May while working on the line where the accident occurred. Terrorism is not suspected, according to news reports.

The Russian Investigative Committee said in a statement that the men have been questioned and charges will be brought soon. The supervisor is Valery Bashkatov and the assistant is Yury Gordov.

"The Investigative Committee intends to establish and bring to justice all those involved into this tragedy, from performers to top officials who had to supervise and ensure the full requirements of the transport safety rules of the Moscow Metro," the statement said, according to CNN.

A power surge is believed to have cause the train crash, as the surge triggered an emergency brake and as a result the subway cars coiled into each other to fill the entire tunnel.

Different reports disagree on the number of those killed in the accident, with BBC reporting 21 and CNN reporting 22. More than 160 people were injured in the wreckage.

The train came off the tracks between the Slaviansky Boulevard and Park Pobedy stations in the west of the city. The train was heading into the center of Moscow when the power surge happened.

Moscow's subway system was tied for third busiest in the world by Travel and Leisure, with 2.46 billion riders each year.

Park Pobedy is 275 feet deep, the deepest station in Moscow, which made rescue efforts more difficult. In addition to the casualties of the accident, more than 1,100 people were evacuated from the tunnel, which was built about 10 years ago.

The metro accident has prompted critics to claim that subway officials have spent too much money extending service and not enough on maintaining the existing lines.