The 52,000-acre Corrour Estate, between Fort William and Dalwhinnie is managed by the Corrour Trust as a conserved wilderness on behalf of Tetra Pak heiress Lisbet Rausing.
A hill-walker has claimed he saw helicopters being used to round up deer to be shot on the estate on October 31, and that the shooting went on for two hours.
For some years the estate has been trying to reduce deer numbers to encourage natural vegetation regeneration without using unsightly deer fencing.
However, under the Deer Act (Scotland), it is an offence to shoot deer from a moving vehicle of any kind, including a helicopter. It is also an offence to use a helicopter to drive deer with the intention of killing them.
However, a spokesman for the estate insisted the helicopters were used only to transport personnel to areas where deer were to be culled and take deer carcasses back, both of which are perfectly legal.
He said: "There was categorically no use of helicopters to drive the deer. Everything was done absolutely professionally and to the letter of the law."
A spokesman for Northern Constabulary confirmed an alleged deer offence in the Lochaber area was being investigated.