Investigators continue to gather details in the case of the poising of a Russian ex-spy and his daughter, who were poisoned . According to British Police it is believe the two victims were first exposed to a rare Russian nerve agent at their front door. On Wednesday British authorities announced the investigation into the attempted murders is now "one of the largest and most complex investigations undertaken by British counterterrorism policing,". Britain has blamed Russia for the attack, igniting a renewed diplomatic tension between Moscow and Western nations. Moscow, continues to vociferously denied any involvement.