Investigators from the Scottish SPCA and officers from Police Scotland swooped on the Millden Estate in the Angus Glens last week.
The £17.5 million estate is considered to be one of the best in Scotland. The investigation is focused on an employee rather than the landowners.
The worker has been suspended while the estate carries out its own investigation.
It is understood that carcasses of protected birds of prey were found during the raid, and dogs were seized. Carcasses of buzzards were seized along with computer equipment.
A spokesman for the estate said: “The estate understands that the investigation by Police Scotland and the Scottish SPCA relates to alleged animal fighting.
“The estate is not the focus of that inquiry. It understands that the inquiry is at a very early stage and is carrying out its own internal investigation.
“In the interim, an estate employee was immediately suspended in accordance with our procedures. The estate will continue to liaise with the appropriate authorities.
“It has a robust system of compliance with the law including a zero-tolerance approach to any wildlife offences or animal welfare issues.”
The raid at Milden Estate was carried out simultaneously to one at an address in Aberdeenshire, as part of the same investigation.
An undercover officer in the SSPCA’s special investigations unit said: “We uncovered intelligence to suggest illegal animal fighting was taking place at these locations.
“With serious concerns about the welfare of both the dogs and wild animals being subjected to this, we worked with the police and external partners to raid both addresses. We’ve seized several animals and will be checking on their condition. Offences such as this are incredibly difficult to investigate as they are very well guarded by those involved.
“Our expertise, in conjunction with the police, has proven to be invaluable to tackling these underground crimes.
“This is the latest in a string of animal fighting cases.
“The society is taking the fight to anyone engaging in this barbaric practice and sending out a clear message that it is not acceptable.”
A spokesman for Police Scotland said: “Officers supported the Scottish SPCA in relation to search warrants at an address in Angus and an address in Aberdeenshire.”