The Liberals say the provincial police unit entered their Montreal headquarters in July.
"(Party) employees present offered their full collaboration," the Liberals said in a statement late Monday.
The announcement comes after a media report, on Radio-Canada, that said police quietly conducted a search for evidence of illegal fundraising.
The Liberals are among several political parties to have been accused of illegal financing during testimony at the province's Charbonneau inquiry into corruption.
The inquiry has heard witnesses from the construction industry describe false-billing and illegal cash transfers to political parties including the Liberals.
In their statement, the Liberals said they have also been co-operating with the Charbonneau inquiry as well as the province's director-general of elections.
The province's corruption unit, known by its acronym UPAC, was created by the former Liberal government in the wake of corruption scandals.
More than 100 people have been arrested on corruption-related charges since the Quebec scandals erupted several years ago, including figures from municipal politics and the construction industry.
A number of those arrests have been preceded by raids.
Radio-Canada reported that the search warrant was sealed immediately after the raid and that it has a court appearance Friday to argue for the warrant, and it's reasons for the raid, to be made public.
The network also reported that it has sources saying some Liberal MNAs received visits from UPAC.
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