So far this year, police have received 26 reports of fuel being stolen from the locked tanks of heavy vehicles in Päijät-Häme alone.
Altogether those reports total up to 14,000 litres of fuel that has gone missing.
"Usually, fuel is stolen directly from station pumps, but this is big league theft that is possibly being organized from abroad," Senior Crime Investigator Jouni Törhönen told Yle.
About a month ago, a routine traffic stop by police discovered a van that contained a hidden 1000 litre fuel tank.
"The methods and the system of tankers is something new to me, but there have been similar cases elsewhere. It strongly looks as if the operation is being directed from Latvia and that only the workers are here," said Törhönen.
According to this investigator, two similar vehicles with large hidden tanks have been found in the Hämeenlinna area. All of the vans have been impounded and suspects are in custody.