Permanent Secretary for Transport and Housing Duncan Pescod is the latest official to be found with illegal structures at his home.
But Pescod said he was unaware that his Sai Kung house, currently being rented out to tenants, had any illegal structures when he and his wife bought it in 2008.
The revelation came after Chief Executive Leung Chun-ying released a statement about the illegal structures at his home on The Peak.
Pescod's house in Las Pinadas, on Clearwater Bay Road, has an illegally built 65-square-foot glass canopy covering a patio and another canopy behind the building.
Pescod, who is also director of housing, said yesterday that they bought the property as an investment and future retirement home.
He said at the time of purchase, just like any other homebuyers who do not have any professional training in building works, they were unaware of any unauthorized structures.
Pescod said they "decorated the property and carried out necessary repairs as requested by the tenants but have certainly not installed any additional structures on the site."
He said with the agreement of the current tenant, a building contractor was appointed to remove the glass canopy and awning on the property, which was done in one day.
Pescod added that the purchase was handled by their lawyers and the property inspected for valuation purposes.
"No adverse reports were received and the concerned bank readily agreed to offer a mortgage on the property."
He added that a thorough check on the building will be conducted and follow-up action taken if required.
Meanwhile, the Buildings Department said inspectors will be sent to the house to carry out checks.
Secretary for Transport and Housing Anthony Cheung Bing-leung said Pescod told him that he did not realize there were illegal structures at the property after he purchased it four years ago since the purchase was handled by lawyers.
Pescod is the latest official to find themselves involved in the row over illegal structures.
Secretary for Food and Health Ko Wing-man was earlier found to have such structures at his home.
In July, it emerged that Ko knocked down an internal wall between the two flats he owns in One Beacon Hill, in Kowloon Tong, without prior permission.
He also built a balcony wall.