Latvian authorities have discovered a tunnel used by migrants to cross the border from Belarus illegally amid long-standing concerns that Minsk is weaponizing migration against the EU.

On Monday, border guards detected 15 people who had come through a 10-meter-long tunnel near the border fence between Belarus and Latvia, Riga’s Interior Minister Jānis Dombrava said Tuesday.

Belarusian ruler Alexander Lukashenko is a close ally of Russian President Vladimir Putin, and his regime has supported Moscow’s war of aggression against Ukraine and taken a hostile stance toward the EU.