NEW YORK (TheStreet) -- Shares of BHP Billiton (BHP) - Get Reportwere falling in mid-afternoon trade on Tuesday after a probe into a November 2015 collapse at the company's Samarco mine in Brazil revealed late yesterday that the incident was caused by drainage and design flaws.

A change in the dam's design between 2011 and 2012 resulted in less efficient water drainage that saturated sand in the dam and led to a loss of strength in the mine, the report revealed.

However, the report did not assign blame or point out particular errors in corporate and regulatory practice as having led to the collapse, Reuters reports.

Co-operators at the mine, Vale (VALE) and Australian-based resources company BHP Billiton, jointly commissioned Cleary Gottlieb Steen & Hamilton to investigate the incident.

"In the wake of this event, we have separately undertaken a comprehensive review of our significant dams, which has confirmed that those dams are stable," BHP's Chief Commerical Officer Dean Dalla Valle said in a company statement.

Shares of Vale were lower in mid-afternoon trade Tuesday.

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