It said wall movements had been detected in the west wall of the south-central portion of the Urucum Central South openpit, with above-average heavy rainfall impacting slope stability.
"We are working with our consultants to make operations safe, with the expectation that mining of the higher-grade gold ore in the UCS pit will start back up again in the third quarter of this year," president and CEO Rob Henderson said.
It said the mill would continue to receive ore from the Urucum North openpit and from stockpiles.
The company expected Tucano's output to drop this year by 10,000 ounces and reduced the mine's guidance to 100,000-110,000oz.
All-in sustaining costs were forecast to increase from US$1,350-$1,450 to $1,450-$1,550/oz.
Tucano accounts for the bulk of Great Panther's production and company's consolidated guidance was also reduced by 10,000oz to 125,000-140,000oz gold-equivalent.
Topia and the Guanajuato Mine Complex (GMC) in Mexico were still expected to produce 25,000-30,000oz Au-eq in 2021.
Great Panther shares (TSX: GPR) closed down 7.84% to C94c, a midpoint in its one-year range of 54c-$1.47.
It's capitalised at $334.1 million (US$277 million).
