According to reports, officials found the highest concentration of the nerve agent on their front door. Investigators did detect traces of the nerve agent Novichok at other locations, but they were at a much lower concentration.
"At this point in our investigation, we believe the Skripals first came into contact with the nerve agent from their front door," Dean Haydon, head of the Metropolitan Police's Counter Terrorism Command, said in a statement. "We are therefore focusing much of our efforts in and around their address."
Officials later noted that searches in around Skripal's home will be stepped up, however, risk to locals remain low. It was also stated that the investigation could last for several months.
Skripal and his daughter are still in critical condition after being exposed to the agent on March 4 in Salisbury, UK. The pair were initially found in a "catatonic state" on a bench before they were transported to a nearby hospital, News Amed reported.
After blaming Russia for the poisoning, UK Prime Minster Theresa May announced on March 14 that 23 Russian diplomats would be removed from the UK. Following May's action nearly 30 countries filed in line and expelled their Russian diplomats, with the majority of the countries being members of the European Union.
Moscow has repeatedly denied playing any role in the Skripal poisoning. Russia says it will respond to the expulsion of the diplomats.