The evidence to the inquiry on Thursday centred on why private security guards were contracted to enforce quarantine and the contracting arrangements with the government.

The inquiry heard Victoria Police, in the first meeting of agencies involved in the program, said private security should be the "first line of security".

In recordings, Emergency Management Commissioner Andrew Crisp said: "I understand that to be the preference of Victoria Police, or the Chief Commissioner, is that private security be the first line of security."

Victoria Police Commander Mick Grainger responded: "Absolutely that's our preference."

Senior jobs department executive Claire Febey said it was her department's role to hire security.

The department's executive director of employment in its inclusion branch, Katrina Currie, was tasked to employ security firms in a little more than 24 hours to oversee the quarantine program, for her "deep knowledge" of employers across the state.

Ms Currie told the inquiry into the quarantine program she had not dealt with security firms before and instead asked for advice from the department's employer engagement team about which firms were "both large and good employers".

Unified was the only firm that was not on a panel of security providers that were part of a state purchased contract for security services.

The inquiry heard Unified was not "preferred" by Trades Hall, after the union representative was asked by the department if the firm paid award wages.

But a jobs department deputy secretary Alex Kamenev told Ms Currie it was too complicated to change security firms.

"You can be blunt and say Wilson have proven very difficult to work with and unhelpful, while Unified have been a dream," Mr Kamenev advised her.

"You should also emphasize, that Unified employ loads of Jobs Victoria clients, so it's actually performing a broader public purpose."

Ms Currie claimed that Wilson Security's "difficulty" was about issues the firm wanted covered-off before they allocated guards. She later conceded under questioning from Wilson Security's lawyer that she had no reason to believe the business was being difficult.

The rationale behind hiring Unified was questioned by members of the jobs department's own staff on March 31, just two days after the hotel quarantine began.

"To have a non-approved firm providing security and effectively enforcing government regulation ... presents significant risk to individuals involved and the department/government that is not easily mitigated," strategic procurement specialist Trevor Esch wrote.

Ms Currie agreed under questioning that Unified Security being Indigenous-owned "added to the picture" as to why they needed an exemption from state contract arrangements.

She wrote in an email to Mr Esch that while Unified Security was not an approved firm, "utlising their services is in keeping with the state government's social procurement objectives of Utilising Aboriginal businesses".

A security guard who was hired by SSG Security, a firm subcontracted by Unified Security to work at Rydges on Swanston, told the inquiry on Monday he was not trained in infection control.

The guard, whose identity was suppressed, said that due to a shortage of personal protective equipment, he was told to use the same PPE for an entire shift.

He said he was told to hide his mask and gloves in his pocket, out of sight of security cameras, when he went on meal breaks.

He contracted COVID-19 while working at the hotel.