Victoria has confirmed 77 more coronavirus cases overnight, its highest numbers yet in the ongoing concerning virus spike.

The cases take the state’s number of active infections to 415.

Of them, 13 are linked to outbreaks, 37 detected through routine testing and 27 under investigation. None are from people in hotel quarantine.

Worryingly, the state now has 20 patients in hospital with the virus, including four in intensive care.

The concerning Victorian numbers come as the Northern Territory earlier announced its first infection in two months. It said it was linked to a person who had flown in from a Melbourne hotspot.

The announcement also followed disturbing claims that Victoria’s hotel quarantine arrangements for returning travellers have been shambolic, including claims that security guards slept with guests.

Companies charged taxpayers for shifts never worked, leading to fewer workers on duty and a higher risk of infections, according a report in the Herald Sun.

Federal Health Minister Greg Hunt urged Victorian authorities to “throw the book” at hotel coronavirus rule-breakers.

“If those claims are correct, then that is completely and utterly unacceptable,” Mr Hunt told Sky News on Thursday.

“We would encourage the Victorian authorities to throw the book either [at] individuals or, if there’s any systemic inappropriate action, at those who are responsible for it.”

The Victorian government has launched a judicial inquiry into hotel quarantine.

Brett Sutton, the state’s chief health officer, refused to be drawn on the claims of hotel quarantine improprieties, saying it was a matter for the upcoming inquiry.

“I did not have any personal information about operations in quarantine, but as I say, it’s entirely appropriate for the judicial inquiry to look into every and all aspects, and I’m sure that will be a process that’s undertaken,” Professor Sutton said.

Tweet from @VicGovDHHS

Melbourne link to NT case

In the Northern Territory, a Darwin resident in his 30s, who returned to Australia from overseas, has become the territory’s first COVID-19 case since April.

NT Health Minster Natasha Fyles said the man was quarantined for two weeks in Melbourne before flying to Brisbane. He flew from Brisbane to Darwin, arriving in the NT capital on Monday.

But before leaving for Darwin, he stayed with family in a Melbourne virus hotspot.

Upon his return to Darwin, he started to feel unwell and was tested for COVID-19. The positive result was confirmed on Wednesday night.

Virus hot spots

Professor Sutton said most of the Victorian cases confirmed on Thursday were in virus hotspots, “but not exclusively”.

“One of the issues is people do move around a little bit. Obviously now, with the restrictions in force, people should be limiting their movement to the fullest extent possible,” he said.

There are stay-at-home orders for 10 postcodes in Melbourne’s inner north and west from Thursday until at least July 29, after the 16th consecutive day of double-digit increase in cases in the state.

Those postcodes are: 3038, 3064, 3047, 3060, 3012, 3032, 3055, 3042, 3021 and 3046.

As in earlier stage-three restrictions, residents are able to leave their homes only to shop for food and supplies, to receive or provide care, to exercise and to study or work if they can’t do so from home.

-with AAP