Three more dental clinics in Melbourne's northern suburbs have been caught operating illegally, according to health regulators, just weeks after it was revealed one man had been working unregistered out of his garage.

Earlier this month the Australian Health Practitioner Regulation Agency (AHPRA) charged Muhammet Velipasaoglu for working as a dentist without a licence for more than a decade.

Since then, AHPRA said it had raided three other properties — at Yaralla Court and Bicentennial Crescent in Meadow Heights and also Preston Avenue, Roxburgh Park — where illegal dental procedures may have taken place.

The practitioners at the clinics have not been arrested or charged, but investigations continue.

"All of these involved potential risk to the public and people who are not registered as dental practitioners," the head of AHPRA, Martin Fletcher, said.

"[At one Meadow Heights property] we found evidence of dental treatment had recently been provided at this premises.

"Because of significant concerns about poor hygiene, inadequate infection control, potential public health risks and substandard care, we immediately advised Victoria's Department of Health and Human Services."

Mr Fletcher said no-one was registered to practise as a dentist the premises and it was unclear how long they had been operating.

It was also unclear if the practices were linked.

He said the latest tip-off came from a registered health practitioner who had seen someone who received treatment at one of the clinics.

"If you received dental treatment from someone at these locations you may have been exposed to risk," Mr Fletcher said.

"We are concerned there appears to be cluster [of unregistered clinics], and that's why we're asking today for people to come forward."

Dr Finn Romanes, Victoria's acting chief health officer, said there was "good evidence that members of our community may have received dental care from unregistered individuals".

"What has been found in at least one case shows a concerning risk of transfer of hepatitis B, hepatitis C and HIV," he said

He said anyone who was concerned about dental work they received, or had any information, should call a health department hotline on 1800 356 061.

Authorities said earlier this month that Velipasaoglu was working in an "unsafe environment, using clinically unsafe equipment" in his home and garage, also in Meadow Heights.

It is believed he was trained in Turkey but had been operating in Melbourne without registration since as early as 2003.

Mr Fletcher said he could not comment on whether those involved in the latest investigation were also trained overseas.