Russian oil giant Lukoil has lost yet another top executive under mysterious circumstances as its vice president died “suddenly” at the age of 53, adding to a spate of deaths of figures linked to the gas and oil industry in the country.

Axar.az reports that the company announced the death of Vitaly Robertus in a brief statement Wednesday, expressing “deep regret” over his death but providing no further details on how he died.

His passing comes after a string of bizarre deaths at the company. Most recently, in late October, Vladimir Nekrasov, the chairman of the company’s board, died unexpectedly of what the company said was acute heart failure. He was 66 and had been brought in to head the board after the previous chairman, Ravil Maganov, plunged from a sixth-floor hospital window and died in September 2022.

Months earlier, in May 2022, another top executive at the company died under strange circumstances. Alexander Subbotin was said to have died of a “drug-induced heart attack,” with Kremlin-friendly media outlets claiming he’d ingested some kind of toad venom while visiting with a shaman.