Russian ex-spy's poisoning in UK believed from nerve agent in car vents; at least 38 others sickened: Sources At least 38 other people in the U.K. were sickened by release of nerve agent.

The Russian ex-spy who along with his daughter was poisoned by a nerve agent in the U.K. may have been exposed to it through his car's ventilation system, sources told ABC News.

Former Russian spy Sergey Skripal and his daughter, Yulia, were found slumped over, unconscious on a park bench earlier this month in the southern English town of Salisbury. The U.K. has accused Russia of bearing responsibility for the March 4 attack, which British officials say involved a military-grade nerve agent of a type developed secretly by Russia.

U.K. officials now have a clearer picture of just how the attack was conducted, sources said. They believe the nerve agent was used in a dust-like powdered form and that it circulated through the vents of Skripal's BMW.

Three intelligence officials told ABC News that the Russian military origin and the nature of the substance, a “dusty” organophosphate, are clear to them.

“It is a Cold War substance, something they claimed never to have,” one senior intelligence official said of Russia to ABC News. Sources said the substance is derived from G- and V-series agents in the 1970s, which are akin to the Novichok nerve agent.

The intelligence officials told ABC News up to 38 individuals in Salisbury have been identified as having been affected by the nerve agent but the full impact is still being assessed and more victims sickened by the agent are expected to be identified

U.S. government chemical warfare experts are also working closely with their British counterparts on what is a major investigation.

“It's seen here as an attempted murder and premeditated,” rather than an attempt just to sicken Skripal with a non-lethal toxin or scare other Russian ex-spies, an intelligence official told ABC News.

Among the more than three dozen sickened by exposure to the agent, most are believed to be suffering minimal symptoms in contrast to the hospitalized Skripal, his daughter Yulia and a responding police officer.

Another possible clue to the poisoning is that sources told ABC News Skripal was shouting and acting incoherently in a restaurant just before he and his daughter collapsed. Such incoherent behavior could be consistent with the early stages of exposure to a nerve agent.

Scotland Yard has released surveillance video of Skripal's car and is asking anyone who saw the vehicle that day to come forward. The police agency declined to comment on new details about the nerve agent attack until it releases information publicly. Julia Macfarlane and Patrick Reevell contributed to this report.