A suspicious fire has destroyed a doughnut shop and damaged a neighbouring ice cream parlour in Adelaide's west overnight.

Key points: It took more than 40 firefighters almost half an hour to extinguish the blaze at the doughnut shop

It took more than 40 firefighters almost half an hour to extinguish the blaze at the doughnut shop Fire cause investigators will examine the scene today, but police say the fire is suspicious

Fire cause investigators will examine the scene today, but police say the fire is suspicious In a separate incident, a man and woman have been arrested for allegedly stealing $10,000 worth of jewellery

The Metropolitan Fire Service said it received multiple triple-0 calls after the Seaview Road shopfront in Henley Beach caught alight about 2:00am.

The fire gutted the doughnut shop and caused minor damage to the ice-cream shop next door, with a total damage bill of about $300,000.

Police say the fire at Lukoumades doughnut shop in Henley Beach was suspicious. ( ABC News: Ben Pettitt )

It took more than 40 firefighters nearly half an hour to extinguish the blaze.

No injuries were reported and fire cause investigators will examine the scene today.

Victorian pair arrested after jewellery theft

In a separate incident, police have arrested a man and a woman after they allegedly stole a necklace and bracelet valued at $10,000, from a Rundle Mall jewellery store.

Police said witnesses reported seeing the man running from a jewellery store and into a waiting car parked on Stephens Place.

CCTV footage revealed the getaway vehicle was a rental car bearing plates that had been stolen from Russell Terrace at Edwardstown earlier in the day.

Further investigations led police to Adelaide Airport where they found the man and his accomplice at the domestic check-in.

A 42-year-old man and a 49-year-old woman, both from Victoria, were arrested and charged with aggravated theft.

They were refused bail and will appear in the Adelaide Magistrates Court today.

The stolen jewellery was recovered and the rental car was seized for examination by crime scene investigators.

Police are calling for anyone with information on either of these incidents to contact Crime Stoppers on 1800 333 000.