The Bulgarian authorities have reopened a criminal investigation into the poisoning of a prominent arms dealer over questions about a possible connection with the nerve agent attack on Sergei V. Skripal, the former Russian spy poisoned in Britain last year.
Bulgaria’s chief prosecutor, Sotir Tsatsarov, said Monday that a suspected Russian intelligence officer, identified in news reports last week as potentially involved in the Skripal case, had also visited Bulgaria in April 2015, around the time that the arms dealer, Emilian Gebrev, was poisoned with an unknown substance.
Last week, the British newspaper The Telegraph reported that the two men indicted in the poisoning — identified by British authorities as active officers in Russia’s military intelligence agency — were accompanied by a third man, an officer using the alias Sergey Fedotov, when they traveled to Britain last spring. In his remarks on Monday, Mr. Tsatsarov said the same man had visited Bulgaria three times in 2015, confirming a report published last week by the investigative site Bellingcat.
“We are trying to establish all moments while he was on Bulgarian territory, the hotels he stayed in, the vehicles he used, contacts with Bulgarian citizens,” Mr. Tsatsarov said at a news conference.
The Russian government has denied any involvement in the attack on Mr. Skripal, and the two Russians named by the British authorities have said they were tourists.
At the news conference with Mr. Tsatsarov, Britain’s ambassador to Bulgaria, Emma Hopkins, who met on Monday with Bulgaria’s prime minister and law enforcement officials, said Britain and Bulgaria had been working closely on the case for months.
“We are working in a joint team and a close partnership, and we are going to find out the facts in this case,” Ms. Hopkins said.
Doctors initially believed that Mr. Gebrev had a stroke after he collapsed at a reception he was hosting in Sofia, Bulgaria’s capital, and slipped into a coma. But when his son and one of his company’s executives were hospitalized with similar symptoms a short time later, the authorities opened a criminal investigation on suspicion he had been poisoned.
Mr. Gebrev, who with the others survived the poisoning, could not be reached for comment. He has told Bulgarian news outlets that he was unsure why someone might want to poison him.
Investigators have so far failed to identify the substance used in his poisoning. Mr. Tsatsarov said a Finnish laboratory, enlisted by Mr. Gebrev, had found traces of organophosphates, which are used in fertilizers, but no evidence of any substances banned by the Chemical Weapons Convention. Investigators also detected a high concentration of chlorine in the arugula that Mr. Gebrev ate in a salad around the time he was believed to have been poisoned, Mr. Tsatsarov said.
The authorities decided to reopen the investigation in October, Mr. Tsatsarov said, after Mr. Gebrev raised the possibility that the substance used in the poisoning could have been Novichok, the same nerve agent used on Mr. Skripal.
Mr. Skripal and his daughter, Yulia, were found incapacitated on a park bench in the town of Salisbury in March 2018. Though emergency personnel at first suspected a drug overdose, it was quickly determined the pair had been poisoned with Novichok, a sophisticated and highly potent strain of nerve agent developed in the Soviet Union. British authorities later said that two officers from Russia’s military intelligence agency, known as the G.R.U., had applied the substance to Mr. Skripal’s front door using a container disguised as a perfume bottle.
Mr. Skripal and his daughter survived and remain in hiding. A British woman who was also exposed to the nerve agent died several months later.
Last week, Bellingcat, which has covered the Skripal case closely, reported that the third officer had traveled extensively around Europe in the years before the Skripal poisoning. He arrived at the seaside resort of Burgas, Bulgaria, on April 24, 2015, Bellingcat reported, four days before Mr. Gebrev was hospitalized.