By Jeb Blount and Brad Haynes
RIO DE JANEIRO (Reuters) - Brazilian iron ore miner Samarco Mineração SA received serious danger warnings from ground sensors in 2014 and 2015, months before a deadly and environmentally destructive burst of a tailings dam, Globo TV's Fantastico news magazine said on Sunday.
The alerts, from probes driven deep into the dam's structure to detect ground moisture and stability, reached as high as "emergency" levels, Fantastico said, citing Samarco-commissioned engineering studies provided to prosecutors investigating the case. The damburst is considered by many to be the worst environmental disaster in Brazil's history.
Samarco, a 50-50 joint venture between Brazil's Vale SA and Australia's BHP Billiton Ltd, is in talks with Brazilian federal and state prosecutors and environmental agencies to settle a 20 billion real ($5 billion) public lawsuit.
Fantastico said the studies did not include sensor data from areas critical to the integrity of recent enlargements to the dam, a sign of scant regard for the sensor data, according to a prosecutor interviewed by the television program.
"It is an extremely grave omission that compromised the operational security of the dam," Carlos Eduardo Ferreira Pinto said. He is investigating the accident for Brazil's Minas Gerais state.
The dam's enlargement, he added, "compromised it in a way that was decisive to its rupture".
The November accident sent a tsunami of mud through hundreds of miles (kilometers) of valleys and rivers, killing 17 people, wiping out small towns, polluting drinking water for tens of thousands and destroying wildlife from the Minas Gerais highlands to the Atlantic Ocean.
A Samarco lawyer told Fantastico the firm followed all dam safety and environmental laws and the area of the dam where sensor data was missing was the most secure part of the structure.
In response to Fantastico's reporting on the missing data, the company that provided the sensor data to Samarco said it was not required to supply data to the government that was within normal parameters.
Vale declined to comment. Samarco and BHP did not immediately respond to requests for comment from Reuters.
BHP has previously said it would release the findings of an external investigation into the dam burst by New York-based law firm Cleary Gottlieb Steen & Hamilton when it is completed.
(Additional reporting by Sonali Paul in Melbourne; Editing by Christian Schmollinger and Mark Heinrich)