An electric motorbike may have caused a large explosion and fire in an Auckland garage.

There was big bang before the double garage at the house on Brighton Rd in Parnell went up in flames just after 3pm.

Senior Fire Investigator Mike McEnaney said firefighters arrived quickly at the scene and the garage was well involved.

He said there were several motorbikes in the garage, and they are looking at an electric motorbike in their investigation.

The garage is completely destroyed - its walls pushed outwards.

Also beyond repair: three expensive motorbikes.

The owner, who wasn't home at the time, is a motorbike collector and is said to be very disappointed to have lost them.

Residents said they heard a huge explosion before the street filled with smoke.

Brighton Road was blocked at both ends while firefighters attended the blaze.

Meanwhile, in a separate incident, guests at an Auckland motel had to be evacuated as a shed fire started spreading to the main building.

Five fire trucks and crew attended the blaze which started in a shed at the rear of the Monument Motor Lodge in Papakura.

The fire was well involved when crew arrived just after 12.45 this afternoon but was dampened down before it spread to the main hotel where guests had been staying.

It only slightly damaged the rear of the motel unit, blistering the paint.

The cause is being investigated.