British police say they believe the Russian ex-spy and his daughter who were poisoned earlier this month were first exposed to a rare Russian nerve agent at their front door.
The investigation into the attempted murders of Sergei Skripal, 66, and his daughter, Yulia, 33, has become "one of the largest and most complex investigations undertaken by British counterterrorism policing," authorities said Wednesday.
The highest concentrations of the nerve agent have been found at the Skripal home, but it has been detected at other locations, according to police.
https://www.nbcnews.com/news/amp/ncna860966