A number of flags were reportedly removed from one of the stands used to house Jags fans at the Energy Check Stadium last Friday, according to the club.
A club statement read: “At around midnight, following Friday night’s match against Rangers, a number of flags were stolen from the North Stand of the stadium.
“The club reported the break in and theft to Police Scotland who are now investigating the matter.”
News of the police investigation comes around two days after an Instagram account with the name ‘bears.rfc’ posted a photo appearing to show three Partick Thistle flags being held up by masked individuals.
More than 8,000 people attended the Scottish Premiership match between Partick Thistle and Rangers, which finished in a 2-2 draw.
The two teams meet again tonight in the Betfred Cup quarter finals in a re-run of Friday night’s fixture.