An ebike shop in the popular tourist town of Byron Bay has gone up in flames.

The fire is believed to have started about 1pm, with thick black smoke soon billowing from the shop on Byron Street.

Passersby quickly flocked to the scene to film the flames, with witnesses seeing many bikes burning inside.

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The shop allows people to rent an ebike for a certain period of time.

Firefighters were confronted by challenging conditions as they tried to quell the blaze.

"Crews have reported possible lithium-ion batteries possibly exploding inside," Fire and Rescue NSW Acting Superintendent Andrew Bickle told the ABC.

It is not known if anyone was in the shop when the fire started.

Police told nine.com.au the fire was not believed to be suspicious, and that it may have been ignited by a lithium battery.

Investigations are ongoing.

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