The landmark Buttercross, in Brigg Market Place, suffered damage to two of its large ornate windows.
We took these pictures on Sunday afternoon, showing wooden boarding over the broken panes within Brigg Tourist Information Centre, on the ground floor.
A request for information has been submitted to North Lincolnshire Council, which owns the listed building, now almost 200 years old.
UPDATE: A spokeswoman for Humberside Police said six glass panes in the Tourist Information Centre were smashed following an altercation between two men in the early hours of Sunday morning, between noon and 1am.
One of them is alleged to have caused the damage.
"No description of the suspect is available," said the spokesman.
"Anyone with information is asked to call 101, quoting crime reference 2201530."
One of them is alleged to have caused the damage.
"No description of the suspect is available," said the spokesman.
"Anyone with information is asked to call 101, quoting crime reference 2201530."
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