(NewsNation) — In the seven months that Russia has waged war on Ukraine, multiple Russian oligarchs have been found dead, several supposedly by suicide or freak accidents.

The mysterious deaths of the men, most of them linked to the oil industry, have raised eyebrows and speculation about whether the Kremlin might have been involved.

Here’s a look at some of the deaths and how the oligarchs died.

• Anatoly Gerashchenko: Fell down stairs

The former head of Moscow’s Aviation Institute died Tuesday after falling down several flights of stairs inside the institute’s headquarters. The organization described the 73-year-old’s death as the “result of an accident.”

• Ivan Pechorin: Fell off boat

The energy executive was “tipsy” before going overboard, according to a Russian news agency. Pechorin worked at the Corporation for the Development of the Far East and the Arctic and was traveling on the boat with some friends in the Sea of Japan. “The death of Ivan is an irreparable loss for friends and colleagues, a great loss for the corporation,” the corporation wrote in a statement. “We offer our sincere condolences to family and friends.”

• Ravil Maganov: Fell out hospital window

Maganov was the chairman of Russia’s Lukoil oil giant and was receiving treatment for an illness when he fell out a hospital window in Moscow, according to reports. The 67-year-old helped Lukoil evolve into one of the world’s largest energy firms, the company said. Maganov was given a lifetime achievement award by President Vladimir Putin in 2019.

• Alexander Tyulakov: Suicide

The 61-year old executive at Gazprom was found dead in the garage of his St Petersburg home Feb. 25, the morning after Russia invaded Ukraine, Russian media reported. Neither Gazprom nor the region’s investigative committee issued any public statements about the death, which newspaper Novaya Gazeta described as an apparent suicide.

• Lenoid Shulman: Stabbed in apparent suicide

Shulman, 60, served as the head of the transport service at Gazprom Invest, which handles investment projects for gas giant Gazprom. His body was found Jan. 30 in the bathroom of a cottage in Vyborgsky district, north of Saint Petersburg, local news reported. A source told RIA news agency his death was believed to be a suicide, and stab wounds were found on his body, according to reports.

• Sergey Protosenya: Hanging

On April 19, Sergei Protosenya, a 55-year-old former top manager of Russia’s largest liquefied natural gas producer Novatek, was found dead with his wife and daughter at a villa in Spain, Russian news media reported. Catalan regional police, investigating the case, have said they believe he killed them and then took his own life.

• Vladislav Avayev: Self-inflicted gunshot wound

Avayev, a 51-year-old ex-vice president at Gazprombank, was found dead in a Moscow apartment along with the bodies of his wife and daughter April 18, Russian media reported. Kommersant newspaper cited investigators as saying they believed Avayev, a well-known banker, had shot both of them before killing himself.

• Vasily Melnikov: Stabbed in apparent suicide

The alpine skier and businessman was found dead in his house in Nizhny Novgorod on March 23. His wife and two minor children were also found dead, all stabbed to death, according to media reports.

Reuters contributed to this report.