Shares in Australian miner Whitehaven Coal fell almost 9% after a fake press release claimed one of the firm's lenders had withdrawn funding.
The release, from an anti-coal action group claiming that ANZ bank had withdrawn $A1.2 billion, prompted the miner to suspend trading in its shares.
Once the hoax was uncovered, Whitehaven shares recovered the losses.
Other Australian firms have fallen victim to hoaxes in recent months.
The statement said that ANZ had withdrawn funding for Whitehaven's proposed Maules Creek mine due to "reputational risks and analysis of the returns on this mine in the current climate of high volatility in the coal export market".
Investors then sold shares in the company, fearing that the mine may be pulled.
Once the hoax came to light, ANZ issued its own release saying it had made no statement on Whitehaven and remained "fully supportive" of the company.
Jonathan Moylan from Frontline Action for Coal, which issued the hoax statement, said environmental concerns had prompted the press release.
"The future of our farmlands, our forests, our health, our climate - these are the biggest threats humanity faces and they are far more important than concerns over liability," he said.