RIO DE JANEIRO — A mysterious oil spill that has polluted shores along a vast area of Brazil’s northeast may have resulted from unspecified criminal activity, and a foreign country could be responsible, President Jair Bolsonaro said Tuesday.

An estimated 100 tons of crude has drifted toward land since early September, polluting some of the country’s most pristine beaches and forcing Brazilian officials to grapple with yet another environmental crisis. The government has already come under close scrutiny, and heavy criticism, after an unusually intense season of forest fires in the Amazon.

Now, oil has been spotted on at least 132 beaches affecting 61 municipalities in nine states, the country’s Environment Ministry said.

Officials have said the state oil company, Petrobras, is not responsible for the spill and that the crude is neither produced in nor exported to Brazil.