The lab's chief added that it only sought to test the chemical used on Sergei Skripal and his daughter, not decide its source. Still, Russia called the remark proof the U.K. is fabricating its claims.
Tensions between Russia and the West are ratcheting up as the Russian Foreign Ministry announced the expulsion of the officials and the closure of the U.S. Consulate in St. Petersburg.
Yulia Skripal was poisoned with her father, Sergei, in an alleged nerve agent attack. While an international dispute has raged, Yulia has been progressing — but Sergei is still in critical condition.
The Metropolitan Police says the highest concentration of the rare chemical was found on Sergei Skripal's front door in Salisbury, England. Investigators assure neighbors that they are safe.
At a summit in Brussels, EU leaders said "there is no plausible alternative explanation" for the poisoning of Sergei Skripal and his daughter earlier this month in southern England.
The cause of death was "compression to the neck," police say. Glushkov was a former close associate of a noted critic of Russia's President Vladimir Putin.
The leaders of France, Germany and the U.S. say, "We share the U.K. assessment that there is no plausible alternative explanation" other than Russia being behind the attack.
Novichok-class agents were developed in top-secret Russian labs at the end of the Cold War. Experts say only Russia is known to have made them. "They've been a deep, dark secret," says one expert.