KIEV, March 30 ??“ Ukraine will investigate why its largest oil company UkrNafta has suddenly started to sell crude oil at 33% discount thus lowering payments to the state budget, officials said Wednesday.

UkrNafta, which was selling its crude at 2,100 hryvnias ($415) per metric ton in October 2005, had resorted to selling the crude at 1,400 hyrvnias in January, Finance Minister Viktor Pynzenyk.