As Melbourne's hospitality venues are being crippled by a string of alleged arson attacks, police and crime experts are scrambling to figure out the motive behind the fires.

Last week, police arrested two teenage boys after an alleged arson attack on Melbourne's Bar Bambi, marking the venue's third suspicious fire this month.

Forensic Behavioural Science expert Dr Lauren Ducat at Swinburne University of Technology says while there is no clear motive behind the alleged attacks, arson is an "effective weapon" for intimidation.

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"It is fast, destructive and highly visible," she explained.

"It sends a message, creates fear and can shut down businesses quickly.

"When offenders see similar tactics succeed elsewhere, that behaviour can be replicated."

She added that the recent alleged attacks would be seriously impacting the confidence of business owners across the state.

"When motives are unclear, there is a sense of unpredictability about the behaviour and uncertainty about how to protect businesses," Ducat said.

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"That can affect confidence for owners, staff and patrons alike."

Ducat added that arson cases can be hard to prosecute as "evidence is often destroyed" and "offenders can flee" quickly after an attack.

"Motivation can be difficult to discern when there are not clear links to the target of the behaviour," she said.

"We often assume there are direct links between target and motive, and when that is not the case, it takes a more nuanced understanding of why people set fires."

Last week's alleged attack appears to be fuelling a mounting underworld war involving hospitality venues across Melbourne.

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Bar Bambi is not the only venue being caught in the crossfire.

Five Molotov cocktails were thrown towards The George Hotel on Cecil Street in South Melbourne on May 2.

Police have established Operation Eclipse to investigate these incidents and whoever is behind them.

The task force has arrested 51 people since 27 April in relation to 38 incidents.

"Thirty-eight of the 51 arrests have been achieved on the hop, so as people were about to commit offences, they've been arrested," Detective Superintendent Jason Kelly said last week.

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"Victoria Police response is working. We are catching people as they're about to commit these offences.

"We're out there every night, every morning, and we're catching them in the act."

Despite making more than four dozen arrests, detectives admit they haven't been able to get to the bottom of who is behind the attacks.

"We haven't had those clear demands from serious and organised crime that you'd expect and that we saw through the illicit tobacco conflict," Kelly said.

"We are keeping an open mind. Everything is still on the table."

"We are working heavily in relation to some avenues of enquiry and that includes offshore [sydnicates]."

Anybody with information is urged to contact Crime Stoppers online or on 1800 333 000.

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