Fitzroy's Bimbo Deluxe will close for a few months after a fire destroyed part of the late-night bar and pizza institution early Wednesday morning.

The Brunswick Street venue released a statement on Wednesday night saying "the extent of damage is still being assessed."

There is also now clarity on the cause of the blaze, which the Metropolitan Fire Brigade said was contained to one upstairs room of the building.

"The fire was caused by faulty office equipment and is in no way suspicious," the Bimbo Deluxe statement said. "Thankfully, no staff or patrons were on site when the fire broke out.

"On the bright side, Bimbos will BRB with a less charred fit in the next few months. We’ll be coming back with a bang, so keep your eyes on the society pages for our big reveal."

It took about 25 minutes and the work of two dozen firefighters to bring the fire under control – flames could be seen spilling out of second-floor windows.