Human rights groups say at least 13 people have already died near the Poland-Belarus border since the start of the summer.
Polish soldiers have found the body of a suspected migrant near the country's border with Belarus.
The remains of a man were found in a forest on Tuesday near the village of Olchowka, local Polish police said on Twitter.
Authorities also recovered a rucksack and a Nigerian passport near the scene, nine kilometres from the border in the municipality of Narewka.
Thousands of migrants -- mainly from the Middle East and Africa -- have been attempting to enter the European Union from Belarus in recent months.
The EU has accused Belarusian authorities of flying migrants in and encouraging them to illegally cross the border in an attempt to destabilise the bloc.
Minsk has denied the accusations and says the EU has failed to facilitate the migrants' safe passage, also accusing Poland of violent pushbacks.
Human rights groups say at least 13 migrants have already died near the Poland-Belarus border since the start of the crisis. But activists have also warned that the death toll could be higher, amid worsening weather conditions.
Humanitarian organisations have also reported that a four-year-old Iraqi girl went missing after being separated from her parents near the Belarus border.
Since early September, Poland’s border zone has been off-limits to reporters and human rights workers, due to a three-month state of emergency and now under new legislation that limits the rights of non-residents to enter the border area. Belarus also restricts the work of independent journalists.
Polish border guards said a group of 35 migrants managed to cross the border with the help of Belarusian soldiers on Tuesday night before they were arrested and sent back.
Last week, the EU, UK, United States, and Canada announced new economic sanctions on the regime of Belarusian President Alexander Lukashenko.
Belarus has also issued retaliatory sanctions on western airlines and has banned certain products.
Meanwhile, the Czech government has approved plans to deploy 150 soldiers in Poland to help guard the country's eastern border. Estonia and the United Kingdom have already mandated troops to help secure the frontier.