The first blaze broke out at a La Porchetta on the Melton Highway in Taylors Lakes about 2.30am on Wednesday.
CCTV footage shows a dark sedan pull up outside the restaurant and two people got out carrying something that appeared to have been a jerrycan, Detective Senior Constable Rhiannon Downs said.
"They may have poured some accelerant over the front of the restaurant and lit it up before leaving the scene," she told reporters on Wednesday.
Flames quickly ripped through the building, scattering debris throughout the restaurant and leaving the shopfront charred.
Minutes later, another fire started at Negroni 888 on Mount Alexander Road in Essendon.
Italian restaurant Negroni 888 in Essendon was severely damaged in the blaze. (Joel Carrett/AAP PHOTOS)
Smoke billowed over the area but firefighters contained the fire to a small section of the venue and stopped it from spreading to a nearby car wash.
No one was inside either restaurant at the time and both were severely damaged by the flames.
Det Sen Const Downs said it was "too early to tell" whether the fires were connected, if they were targeted attacks or had anything to do with more than 40 arson attacks linked to a conflict over illegal tobacco.
"Obviously, businesses don't just light themselves on fire so it will form part of our investigation as to what the motive is behind this," she said.
A family ran the popular Taylors Lakes restaurant and are devastated by the fire, Det Sen Const Downs said.
"The impact that it's going to have on this family and this community far outweighs any monetary damage that they've done here, it's atrocious behaviour," she said.
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