Five North Korean construction workers were found dead in their accommodation in the Russian city of Ufa on Thursday morning, an investigative committee of the Republic of Bashkortostan reported.

According to the committee, an initial assessment indicated that the North Korean workers died of carbon monoxide poisoning after burning coal in a trailer in an attempt to keep warm when their heating broke.

Temperatures on the night of February 28 to March 1 hit a low of -24 degrees Celsius (-11.2 degrees Fahrenheit), according to accuweather.com.

“In the morning of March 1 of 2018, law enforcement agencies of the republic