Less than 1% of the flow meters checked at Bulgarian filling stations over the past three days have been found to be either tampered with or showing incorrect readings, the Economy Ministry said on Sunday.

The announcement was made after Prime Minister Boyko Borisov on Wednesday ordered inspections of filling stations across Bulgaria over suspected manipulation of data about the quality and quantity of motor fuels sold at the pump.

Out of 10,862 flow meters checked by metrology experts, 87 have been either found to show readings higher than the actual volume of fuel filled into car tanks or had their anti-manipulation seals tampered with, the Economy Ministry said in a statement.

Fifty-three of those problematic meters were found at small filling stations while the remaining 34 were found at outlets of big chains, according to the statement.

Another 138 flow meters remain to be tested early next week before the Economy Ministry can report that it had checked all fuel measuremement devices at Bulgaria's filling stations.

Based on the results of the inspections, the Economy Ministry will propose amendments to the regulations governing the operations of the State Agency for Metrological and Technical Surveillance and the Bulgarian Institute of Metrology to avoid overlapping of their functions and improve controls.

There were 3,105 filling stations in Bulgaria at the beginning of the year, according to official data.