UPDATED 1.30PM:  The Fire Service says a blaze at a cafe on Auckland's North Shore this morning was accidental.

The fire caused extensive damage to the storeroom of Beach Bistro at Browns Bay and smoke damage to the cafe.

Residents from Ocean Breeze Apartments, which is above the cafe, had to be evacuated because of the smoke and one elderly man was rescued by firefighters.

Specialist fire investigator Gary Beer is investigating some electrical equipment in the storeroom of the cafe.

"We're just looking at things such as multi-plugs, extension cords and computer-type equipment in the room."

Meanwhile, those in the apartments above the cafe have been allowed back inside the building.