Britain and Bulgaria are investigating a third suspect in the Salisbury chemical attack who has also been linked to a 2015 poisoning in Bulgaria, the British ambassador to Sofia said on Monday. Britain's ambassador Emma Hopkins made the comments after talks with Bulgarian Prime Minister Boyko Borisov and Chief Prosecutor Sotir Tsatsarov. "We are continuing a close partnership together with a joint team looking into the factual underpinning of these allegations," Ms Hopkins said at a televised news conference. A report published last week by the investigative website Bellingcat identified a hitherto unknown third suspect in last year's attack in the English city of Salisbury on former Russian spy Sergei Skripal and his daughter. Both had to be hospitalised after being exposed to the highly toxic nerve agent Novichok in an attack the British government says was "almost certainly" approved by the Russian state. According to Bellingcat, the third suspect is a Russian military intelligence officer known under the alias "Sergey Fedotov". The site said Fedotov had arrived in Britain two days before the Skripals were poisoned and was possibly involved in the attack. Bellingcat has already used open-source techniques to identify two Russian military intelligence officers, Anatoly Chepiga and Alexander Mishkin, accused by Britain of carrying out the attack. Despite Russian denials that they were involved, both men are now the subject of EU sanctions.