A fire at Anglesey Aluminium, one of north Wales' biggest employers, has left production at one-third of normal, the owner has confirmed. It could be up to three months before full production returns following the blaze on 12 June. Owner Rio Tinto said a full investigation into the cause of the fire was under way. About 540 people work at the plant, which produced 148,000 tonnes of hot metal in 2007. A Rio…