Dewsbury Museum has been forced to close after a ceiling was damaged.
The damage was discovered by staff over the weekend and because of its location, access to the main museum is not possible.
Kirklees Council said work to investigate the damage and create a safe access into the main building whilst repairs are carried out is now underway.
The education room is unaffected and events already planned are expected to be able to go ahead.
There is a separate access to the museum shop and this will remain open.
It is not known how long the museum, in Crow Nest Park, will remain closed.
The Grade II listed museum and art gallery re-opened in August 2010 after and extensive programme of refurbishment and restoration.
Original features such as wood panelling, ornate ceiling work, fireplaces and mullioned windows were revealed during the work. Parts of the building date back to the 16th Century.