The company would assess the case, announced by Brazil's environment minister on Friday night, once it has been filed, a company spokesman said.
BHP is "committed to supporting Samarco to rebuild the community", he added.
The Brazil government said it will sue mine operator Samarco, co-owned by BHP and Brazilian iron-ore producer Vale.
The lawsuit will be filed on Monday, according to attorney general Luis Adams.
At least 13 people died and a village was destroyed when a dam burst at the mine earlier this month.
BHP and Vale announced an Emergency Fund on Friday to help with the recuperation of the Rio Doce river, but has not revealed the size of the fund.
"The total cost of damage has not been calculated yet," the BHP spokesman said.
The dam's collapse led to millions of tonnes of mud and waste entering the river and trailing 500km into the Atlantic Ocean.
The company agreed last week to pay the Brazilian government $260m (Â£170m) in compensation, and has already been fined $66.3m (Â£43.6m) by Brazilian environmental agency Ibama.
BHP has said the waste water in the dam, a by-product of iron ore extraction known as tailings, does not pose any threat to humans.
Mining giant BHP is bracing itself for a $5.2bn (Â£3.4bn) lawsuit from Brazil's government over the devastating collapse at the Samarco iron-ore mine.