Poland wants to tighten trash-import rules after the country become a magnet for European Union waste materials in the wake of a ban on sales to China.

The move, announced by Prime Minister Mateusz Morawiecki on Tuesday, follows a plague of fires at Polish landfills, seen as potential foul play by the government as companies seek to cut corners on recycling rules or clear space for new deliveries of trash.

The dumping-ground fires appear to be “a coordinated action,” Morawiecki told a news conference in Warsaw. “There are all kinds of reasons to assume this isn’t a coincidence.”

Poland is starting an investigation into the several dozen trash-heap fires this year, which occurred as refuge imports from western Europe intensified. Environment Minister Henryk Kowalczyk said there were about 120 illegal landfills in the country, which imports about 400,000 tonnes of waste per year. The value of illegal imports alone is estimated at some 1.5 billion zloty ($400 million), he said.