Stakes in the government’s crackdown on Greece’s billion-euro illegal fuel business appear to be getting higher after a number of samples of suspected diluted fuels were tampered with by thieves at the state laboratory yesterday.

The Finance Ministry said that the burglars broke into the state laboratory in Piraeus and stole the details of each sample which had been tested, in an attempt to make it impossible for authorities to identify the source of the fuel.

However, it appears that the government was a step ahead, as the tests had already been performed, filed and sent on to the next stage of the investigation.

“Of the research conducted by the state laboratory... the results of the testing had already been sent to the relevant authorities (such as prefectures) for further action,” the ministry said.

The conservative government has been trying to stamp out the country’s booming illegal fuel business, which costs the state billions of euros every year in lost tax revenues.

One of the largest problems is that petrol providers dilute tax-heavy car fuel with heating oil that has a lower tax rate or even water and sell the mixture on to motorists as regular gasoline. Tests have shown that pollutants from this mixed fuel are far more dangerous to human health than those created by regular legal petrol.

The government said yesterday that it will triple its checks on petrol stations in Athens and other parts of the country. Around 1,250 checks will be performed in Attica each month and 1,750 in the rest of the country.

Additionally, more on-the-spot checks will be conducted on professional vehicles, such as trucks and buses.