LONDON: British police have identified more than 200 witnesses and are looking at more than 240 pieces of evidence in their investigation into a nerve agent attack on a Russian ex-spy and his daughter, interior minister Amber Rudd said on Saturday. Former double agent Sergei Skripal, 66, and his daughter Yulia, 33, have been in hospital in a critical condition since Sunday, when they were found unconscious on a bench in the southern English cathedral city of Salisbury. “The two victims remain in hospital and they’re critical but stable,” Rudd told reporters after chairing a meeting of the government’s Cobra security committee. Skripal betrayed dozens of Russian agents to British intelligence before his arrest in Moscow in 2004. He was sentenced to 13 years in prison in 2006, and in 2010 was given refuge in Britain after being exchanged for Russian spies. Many in British media and politics have speculated that Russia could have played a part in the attack on Skripal, but Rudd reiterated that it was too early to say who was responsible, and police should be given the time and space to determine the facts. The Kremlin has denied any involvement in the incident and accused the British media of whipping up anti-Russian hysteria. But some in Britain say the nerve agent attack fits a pattern of suspicious Russian-related deaths in the UK and in the United States, and are calling for a high level police investigation into whether Britain has become a killing ground for the state-sanctioned elimination of foes of the Russian government. The brazen assault has not been formally blamed on the Russian government, but it is raising hard questions on how to deal with Russia’s increasingly aggressive stance — even as officials in the US are trying to determine how to respond to Russian interference in US elections. Several politicians, analysts and intelligence agencies believe the case of Skripal, who moved to Britain after he was freed in 2010, may prove to be the work of the Russian government, Russian organized crime groups, or a fluid alliance of the two. “Russian leaders seem to go out of their way to get rid of anybody that seems to be in their way, someone who’s betrayed them, someone who’s interrupting the money flow, and they don’t seem to care about borders, they just go wherever they have to go to get their guy,” said Joe Serio, the American author of “Investigating the Russian Mafia,” who spent nearly ten years with the anti-organized crime unit of Moscow’s police. “Britain happens to be one of the central places where Russians flee. It’s the gateway to the West, the seat of the language, the seat of the empire, the seat of major finance,” he said. Yvette Cooper, chairwoman of the Home Affairs committee in Parliament that reviews police and intelligence matters, and Ian Blair, former head of the Metropolitan Police that is spearheading the inquiry, both said this week that a string of unexplained deaths must be investigated in light of the latest attack. Cooper cited a BuzzFeed News investigation into 14 deaths that may have been the result of foul play. “No attempt on an innocent life on British soil should go uninvestigated or unpunished,” said Cooper, who called for the National Crime Agency to scrutinize the 14 deaths in light of reports that US intelligence officials believe they may be linked to Russia — even though British police have not reached the same conclusion in most cases. There was also a chilling message from Moscow in the days after the attack on Skripal, delivered by a Russian state television news anchorman who warned potential double agents they should expect a shortened life span in Britain.