A seagull may be the arsonist behind a blaze which gutted a luxury seafront penthouse.

Fire investigators think the bird may have picked up a burning cigarette butt, dropping it on to wooden decking on the flat's balcony when it realised it wasn't food.

Two other unusual theories are being explored.

The sun's rays passing through balcony glass may have heated up decking until it burst into flames.

A stray seafront firework is also a possibility.

Baffled experts were ruling nothing out as they continued investigating Monday's fire at the Van Alen building in Marine Parade, Brighton.

Station Officer Spencer Bartley, in charge of firefighting at the scene, said the blaze was unusual in that it started on the balcony and worked its way inside, wrecking the interior.

Flames leapt 30ft from the balcony of the vacant £750,000 three-bedroom flat just after midnight.

About 20 residents in the seafront block, once home to Spice Girl Emma Bunton, were evacuated.

Frank Davis, East Sussex Fire Brigade Assistant Divisional Officer, said the seagull theory was a "definite possibility".

He said balcony glass was possibly to blame and, although the fire started late at night, heat could have built up through the evening.

He said: "Any one of the explanations is possible. We won't know until our investigation has been completed."