Ski area manager Hamish McCrostie told the Queenstown Times this week there had been a couple of close calls already.
"These areas are fenced off and signed, and unauthorised persons should keep out. The construction guys are careful with what they are doing, but it's a safety issue that we have concerns about."
More than 10 people a day ignore the warnings and climb the Big Easy track.
The bottom of the track is being widened and flattened to improve access to the Meadows Express chair lift, as well as the construction of a new novice trail.
All of the mountain bikers approached by staff were New Zealanders.
Mr McCrostie said that mountain bikers could still access the M1 track and exit via the Rocky Gully Rd.
"It should be finished by the end of February, but throughout the summer there is machinery moving around on the mountain," he said.
