Burglars stole thousands of pounds worth of items from Horbury’s Carr Lodge mansion.
The intruders took exercise equipment, original prints and oil paintings plus copper piping.
Police said the break-in of the 18th century building took place sometime between Wednesday, January 14 and Friday, January 16.
PC Alex Booth, from Wakefield District Police, said: “The house is a piece of local history, which is currently in the process of being renovated, and this kind of incident is damaging to the local community.
“Several thousand pounds worth of items were taken and it is likely that those involved will have had a vehicle parked nearby to load property in to.
“It is possible that this burglary has happened during daylight hours with the offenders purporting to be workmen and that someone who was in the area may have seen something suspicious but not quite realised it at the time.
“I would ask anyone who may have been in the area of Carr Lodge between Wednesday and Friday last week to cast their mind back and if they did see anything that may assist the investigation to contact police.”
Anyone with information should contact Wakefield North West Neighbourhood Policing Team on 101 and quote the crime reference 13150021612.