Italian police and Europol say eight people have been arrested in a half-dozen European countries for allegedly operating a diesel import scam that avoided taxes by disguising the fuel as it transited across the continent.

Italy's financial police said Thursday that the scam netted 5.7 million euros ($6.2 million) as some 4,000 tons of fuel entered the country to be sold on the black market without paying diesel-related sales taxes.

The operation involved transporting the fuel in plastic storage tanks made for holding water, not flammable diesel oil, and adding chemicals to them to make it seem they were carrying lower-taxed lubricant oil, not diesel.

Europol said the scam, which operated in Italy, Britain, the Czech Republic, Germany, Romania and Malta, involved companies that provided false invoices and transport documents.