The Los Angeles Times reports that the workers, six from polling firm Consulta Mitofsky and three from Parametria, had been working near the agricultural town of Apatzingan, where there have recently been heavy shootouts between police and drug-cartel members.

Michoacan state prosecutor Jesus Montejano said in a radio interview that the nine were in “a good state of health” but did not provide details on who had been holding the pollsters. No ransoms had been paid for their return either, he said.

Consulta Mitofsky chairman Roy Campos posted on Twitter: “Yes, it’s been confirmed, I celebrate the release of the six persons that were doing polling, I do not celebrate that they had several days taken from them.”

Parametria director Francisco Abundis said that the three workers from his firm were “safe and sound”.