Tenants living at the rear of a much-loved vintage shop have fought to try to save it from flames for a second time in as many weeks.

Fire broke out at the Wonderbox store on Beach Rd at Christies Beach, in Adelaide’s beachside south, just before 3am on Thursday.

The tenants tried to put the fire out with nearby hoses but the flames proved too intense.

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The fire took hold of the whole building before emergency crews could respond.

The store was filled with vintage goods such as old radios and “just things you can’t replace”, the owners said.

The fire has devastated the owners of Wonderbox. Credit: 7NEWS

Owners Brenda McDermott and Kylie Shortridge are both devastated over the loss.

“Complete devastation, we worked so hard,” McDermott told 7NEWS.

It is the second fire at the business in two weeks, after petrol was poured on the airconditioning unit and set alight.

That fire was extinguished before it spread.

But this time they were not so lucky and the shop was totally gutted.

Damage is estimated at $800,000 but the owners are not insured.

The store was full of giftware and jewellery when the fire broke out. Credit: Google

Police and fire investigators are now looking into the cause of the latest fire, and whether an arsonist or arsonists may be responsible for both blazes.

Both fires have been deemed as suspicious.

“I just can’t believe someone would target us in that way, it’s just awful,” Shortridge told 7NEWS.

“We had so much stuff in our shop, stuff that we had handmade ourselves.

“I would love someone to come forward if they have any information and get the buggers that did it,” Shortridge said.

Anyone with any information is urged to contact police.

The fire gutted the Wonderbox store. Credit: 7NEWS