TORONTO (Reuters) - Environmental activists have occupied an expansion site at an upgrader majority owned by Royal Dutch Shell Plc, Greenpeace and the company said on Saturday, the third such protest in recent weeks to target facilities linked to oil sands production.

Greenpeace said 19 activists scaled an under-construction upgrader at Shell’s Scotford facility in Fort Saskatchewan, Alberta to protest “the climate crimes of the tar sands.”

A statement from the environmental group said two protesters had been detained.

Shell said in a statement that no construction was going on when the protesters entered the site and production at the refinery and upgrader are not affected. The upgrader is also owned by Marathon Oil Corp and Chevron Corp.

“We are working with the RCMP (Royal Canadian Mounted Police) and government authorities are being notified,” Shell said.

Upgraders are part of the process that converts tar-like bitumen mined from the oil sands into usable crude.

The protest comes after environmental activists last month canoed into Suncor Energy Inc’s oil sands operation in northern Alberta, blocking equipment.

In another incident, protesters chained themselves to equipment at a Royal Dutch Shell oil sands mine in northern Alberta to highlight what they view as excessive greenhouse gas emissions from the region’s oil production operations.