Lukoil confirmed the death of its chairman on Thursday in a statement posted on its website. Ravil Maganov “died after a serious illness,” Lukoil said, without mentioning a fall. “Maganov contributed enormously to the development of not only the company, but the entire Russian oil and gas sector.” Lukoil, Russia’s second-largest oil and gas company, made headlines in March when it called for “the earliest possible end to the armed conflict” in Ukraine. “We express our sincere sympathy to all the victims affected by this tragedy,” the company’s board of directors said in a statement to shareholders, staff and customers at the time. “We strongly support a lasting ceasefire and a settlement of the problems through serious negotiations and diplomacy.” The company produces more than 2% of the world’s crude oil and employs over 100,000 people. RIA Novosti cited a law enforcement source as saying on Thursday that Maganov “probably committed suicide.” “Investigative authorities are working on site to ascertain the causes of the incident,” the source told RIA. At least five prominent Russian businessmen have reportedly killed themselves since late January, according to previous CNN reports.