Media reports say workers from survey firm Parametria are the latest to have vanished while working in Apatzingan, the same town where six Consulta Mitofsky pollsters disappeared over the weekend.

The town is said to have been the site of recent violent clashes between security forces and a major drug-trafficking gang.

In an LA Times report, Parametria director Francisco Abundis explained how the company had sent a team of 25 to the town to carry out surveys for the Democratic Revolution Party. Colleagues noticed that three of their number were missing on Monday.

Abundis said that workers in Michoacan had been told to avoid areas they thought were too dangerous, but didn’t consider Apatzingan to be one of them. “We had been in this same municipality a month ago without a problem,” he said. “That’s why it surprised us.”