Shares in miner BHP Billiton Ltd tumbled after Brazil's Federal Public Prosecution said it had launched a $43 billion civil suit for a dam break that killed 19 people and caused the worst environmental disaster in the country's history.

BHP said Wednesday the suit seeks social, environmental and economic compensation in relation to the failure of the dam at the Samarco iron ore operation. Samarco is a joint venture of the giant mining companies Vale of Brazil and BHP Billiton of Australia.

The dam failed in November and unleashed a flood of toxic mud that destroyed several towns, killing people and damaging the environment.

BHP said it remains committed to helping Samarco to rebuild the community and restore the environment.

Shares were down 9.4 percent to 18.79 Australian dollars ($14.24).