PHOENIX (AP) â¿¿ Authorities said Wednesday that a theft of copper plates from a southern Arizona plant was far more extensive than they originally thought, dating as far back as 2006 and totaling more than $10 million. It had been believed the thefts began in April 2012, but officials with the state Department of Public Safety said they served search warrants Wednesday on recycling businesses in Tucson and Nogales to look for possible transaction records from earlier years. The DPS earlier recovered $1.5 million in copper plates stolen from the Asarco mine in Hayden, but agency officials said thefts of copper may have totaled more than $10 million. The initial investigation began in September when it was discovered that a group of people was stealing large amounts of copper anodes from the mine, DPS officials said. At that time, it was believed that about 700 anodes were stolen. DPS said 488 anodes have been recovered. DPS officials said its investigators have identified three possible exporters of the stolen copper. Search warrants were served on recycling companies that may have retained records of the transactions, according to the DPS. The agency identified the companies as Mariposa Recycling in Nogales and its parent company Recyco Inc., which has two locations in Tucson. An official at Recyco declined to comment Wednesday.