Polish soldiers have found the body of a man next to a backpack and a Nigerian passport in a forest close to the Belarusian border, the police said on Wednesday.
Around a dozen migrants have been found dead along the border since thousands of people, mostly from the Middle East and Africa, began trying to cross in the summer.
Aid groups warn the toll could be even higher and say freezing conditions make the crossings particularly dangerous.
“The body was found in a forest near Olchowka in the Narewka commune yesterday,” local police said on Twitter.
The border guards also said a group of 35 migrants managed to force their way across the border in the night between Tuesday and Wednesday with the help of the Belarusian military.
The migrants were all detained and sent back.
The West accuses Belarus of engineering the crisis in an attempt to pressure the EU, which has imposed sanctions over the regime’s crackdown on the opposition and independent media.
Belarus denies this and has urged the EU to take in the migrants.