The two New Gold employees received medical care for non-life-threatening injuries while a contract driller is presumed dead.
New Gold said in a statement the on-site emergency management system had been activated and the Royal Canadian Mounted Police service and provincial safety authorities were notified.
Operations at the mine have been suspended pending an investigation. The company did not say how long the suspension would last.
New Afton reported six COVID-19 cases in the December quarter, five among contractor teams. All six cases are said to have recovered.
New Afton achieved the mid-range of its revised 2020 gold-equivalent guidance of 190,000-220,000oz at 204,416oz.
The mine near Kamloops has proven and probable reserves of 1 million ounces gold, 2.8Moz silver and 802 million pounds copper.
New Gold also operates the Rainy River gold mine in Ontario.
Shares in New Gold (TSX:NGD) dropped as much as 9% on Tuesday to C$2.40, capitalising it at about $1.6 billion (US$1.25 billion).