MARIANA, Brazil, Nov 12 (Reuters) - President Dilma Rousseff on Thursday flew over a devastated part of Brazil's southeast region where two dams burst at an iron ore mine last week, killing at least seven people and swamping a vast area with mud and mine waste.
Her visit comes as federal prosecutors said Wednesday they would work with state prosecutors to investigate possible crimes behind the disaster, and the country's mining minister said the government would conduct an audit of other dams in the sector.
The moves by federal officials toughen the discourse of a national government that until recently had left much of the response to the disaster in the hands of the state government of Minas Gerais, a global mining hub and site of the tragedy.
On Wednesday, Rousseff, a native of Minas Gerais, spoke with the chief executives of BHP Billiton Ltd. and Vale SA , the mine's owners.
She told them Brazil's government expected the companies to pay for rescue and cleanup efforts, as well compensation for more than 500 people who were displaced as their homes were destroyed. Earlier, her environment minister said the government was mulling fines against the two industry giants.
On Wednesday, a top federal prosecutor said the federal government would form a task force with Minas Gerais prosecutors to see if federal crimes may have been committed in addition to violations found by the state, responsible for the environmental licensing.
"Vale and BHP were completely careless in terms of prevention," said Sandra Cureau, an assistant prosecutor general in Brasilia, Brazil's capital. "There has been a total lack of concern with the victims."
Rousseff was expected to speak Thursday after surveying the disaster area.
State authorities said 19 people were still missing and most were likely buried in the heavy trail of sediment that was disgorged when the dams burst last Thursday. At least two other bodies await identification, possibly lifting the death toll to nine.
Contaminated waste from so-called tailing ponds, mineral waste that was stored in reservoirs contained by the dams, was flowing through two states, interrupting the water supply of hundreds of thousands of people and raising questions about the potential impact of the waste on residents' health, agriculture and the ecology of the region.
On Wednesday, the chief executives of BHP and Vale apologized for the disaster and said they would fulfill their obligations as owners of the mine, formally operated by their joint venture Samarco Mineração SA.
The mine employs about 1800 people, 13 of whom are among the believed victims, and is responsible for about 10 percent of Brazil's iron ore exports.
The federal government has authorized an additional 9 million reais ($2.36 million) to the mines ministry for an audit of dams in the so-called iron quadrangle, the heavily mined region in Minas Gerais where the Samarco mine operates.
Additional reporting by Anthony Boadle in Brasilia; Writing by Paulo Prada; Editing by Bernadette Baum