UPDATE 1-Brazil prosecutors file $44 bln lawsuit against Vale, BHP for dam spill

RIO DE JANEIRO, May 3 (Reuters) - Federal prosecutors in Brazil filed a 155 billion-real ($43.5 billion) civil lawsuit on Tuesday against iron miner Samarco, and its owners, Vale SA and BHP Billiton, for a collapsed tailings dam in November that killed 19 people and polluted a major river.