Four passengers have been fined £10,000 after failing to state they had come from a coronavirus "red list" country within the previous 10 days.
Travellers arriving in England from one of 33 countries on the list must now quarantine in a hotel for 10 days.
These include places such as Portugal, the United Arab Emirates, and South American countries.
The passengers were stopped at Birmingham Airport after attempting "to hide their routes".
Temporary Assistant Chief Constable Chris Todd told a meeting held by the West Midlands Police's strategic policing and crime board: “By midday yesterday (Monday), on the first day of implementation, we have received six passengers who had declared travelling from a red list country, who were taken to the quarantine hotel.
“We also had four passengers who were identified as having travelled from a red list country, that hadn’t declared it.
“So there are some people who have who have attempted to hide their routes but that’s not worked out.
“They were identified and received £10,000 fines as a result.”
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The government is using nearly 5,000 rooms across 16 hotels – with another 58,000 on standby – to carry out the quarantine.
Those who travel from red list countries must quarantine in the hotel room but can leave for urgent medical help, exercise or a funeral of a close family member – provided they have "been given prior permission by a person authorised by the secretary of state for this purpose”.
Failing to quarantine can result in the £10,000 fine, while those who lie on their passenger locator forms face up to 10 years in prison.
Those who have not travelled to England from a red list country must still provide a negative COVID-19 test from within 72 hours before they departed, quarantine for 10 days at home and complete two tests after arriving.
Scotland's stricter regime – which requires all visitors from abroad to quarantine in a hotel – has led to accusations of a loophole that could allow people from non-red list countries to arrive in England then travel up over the border.
First minister Nicola Sturgeon declined to rule out shutting the border, if deemed necessary, on Monday.
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