Criminals are selling fake COVID-19 test certificates in Europe's major airports and stations.
That's according to Europol, the European Union's police agency.
It said fake negative certificates were found being sold in airports and stations in France, the UK and Spain.
It comes after several European countries told incoming travellers they needed a negative test result to enter their territory.
A man in the UK was arrested outside London's Luton Airport in January on suspicion of fraud by false representation, in relation to the sale of counterfeit test results, Europol said.
A woman and six men were arrested in November for selling false certificates to travellers at Paris’ largest airport, Charles de Gaulle. Prosecutors said the fake certificates were being sold to travellers for between €150 and €300. The suspects face up to five years in prison and a maximum fine of €375,000 if convicted.
In December 2020, a fraudster was apprehended by Spanish police for selling fake test results for €40.
"Given the widespread technological means available, in the form of high-quality printers and different software, fraudsters are able to produce high-quality counterfeit, forged or fake documents," Europol warned.