Armed robbers made off with 7,000 ounces of gold worth $8.5 million at current prices from Canadian firm McEwen Mining`s mine in Sinaloa, Mexico, the company said.
"The crime is being vigorously investigated by the Mexican authorities," McEwen Mining said in a statement late Tuesday.
The loot -- gold-bearing concentrate -- weighed approximately 900 kilograms (almost 2,000 pounds).
The Toronto-based company added that its insurance would cover part of the loss from its El Gallo 1 mine, but not all of it.
McEwen Mining is led by Rob McEwen who previously steered Vancouver`s Goldcorp to become the world`s fourth-largest gold-miner.