Lam on Saturday said the authorities had found at least four returnees who had violated the home quarantine order. They had been sent to the government quarantine camp and would face prosecution later.

Earlier, three Hongkongers returning from mainland China were also prosecuted for breaching the order. Their cases would be heard next week.

The chief executive warned people defying the rules they would face “zero tolerance” from the government. They will be prosecuted without warning, she said.

The maximum penalty is HK$25,000 fine and six months imprisonment.

Earlier, some overseas returnees posted photos on social media showing how they removed a tracking wristband authorities used to monitor their movement. Hongkongers coming back from overseas need to follow a 14-day home quarantine order.

The authorities had dispatched more than 11,000 wristbands on the first two days, according to the health authorities.

The wristbands are paired to a mobile app downloaded by returnees. They have to use the app to scan the QR code from time to time to report their locations.

The Office of the Government Chief Information Officer (OGCIO) is responsible for the technical support of the wristbands.

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Lam on Saturday also said she had asked law enforcement agents to conduct more spot checks to deter people from defying home quarantine.

Concerns have been raised over the effectiveness of the quarantine measures.

In one viral social media post, a person showed off how she managed to remove her wristband, with a caption saying “it took me the entire day”.

Another post said “cut your wristbands and leave the phone you downloaded the app with at home together”, suggesting this as a way for people under quarantine to head out without being noticed by officials.

A man who gave his name as Stanley Lee and was given a wristband after recent travel, said the wristband could be removed with minimal effort.

“If I add a bit of cream and try to slide it a bit, I should be able to take it off,” said Lee, whose wristband slipped off unexpectedly while he was speaking to the Post.

He said the wristband was basically a piece of plastic printed with a QR code, a bar code readable by smartphones that can transfer website links and other digital information.

“It’s not connected to any battery … technically I can leave home without my phone [which shares the location],” he said.

While Lee could leave his home without being noticed, he said he had no plan to do so.

“It’s part of the civic duty. I can’t be 100 per cent sure I am free of virus,” he said.

A source involved in the quarantine system said cutting the band would not trigger an enforcement response in itself.

“If four people were quarantined at home together, one could stay at home to [help scan other people’s removed wristbands] and the other three could go out shopping,” the source said.

A spokeswoman from the OGCIO said the mobile app could determine the location of the phone based on nearby signals such as Wi-fi and Bluetooth. If the phone has left the designated quarantine area, the app would prompt the person to scan their wristband.

She explained that if the person was not able to scan the band within a minute of a request, the Department of Health and police would be alerted and approach the person.