Six North Korean nationals were killed when a train hit their vehicle in the Russian Far East on Sunday, with local authorities launching a criminal probe into the accident.

The collision took place in Russia’s Jewish Autonomous Region, killing six of the seven North Korean passengers on board, the state-run RIA news agency reported, citing law enforcement sources.

Local investigative authorities said they opened an investigation into the accident but did not disclose the passengers’ nationality — a common practice among Russian authorities amid heightened scrutiny of illicit labor imports.

The regional government similarly stopped short of confirming the