UPDATE 1-Brazil's Samarco, owners hire banks for debt talks -source

SAO PAULO, June 20 (Reuters) - Brazilian mining company Samarco Mineração SA and owners Vale SA and BHP Billiton Plc have hired banks to sound out creditors on a potential renegotiation of $3.8 billion in debt, after a deadly dam spill led to the shutdown of a key mine, a source with direct knowledge of the plan said on Monday.