North Korean hackers made off with nearly $41 million worth of cryptocurrencies from an online casino and sports betting site this week — money officials worry will be used to bolster the country’s nuclear weapons program ahead of an expected arms deal with Russia.

The FBI announced on Wednesday it had traced the hack of Stake.com back to North Korea and its state-sponsored Lazarus Group, which has stolen more than $200 million in cryptocurrencies over the past year alone.

The White House has previously warned that North Korea was shipping artillery shells and rockets to Russia, and were set to negotiate for more arms deals.