The former Russian spy who was poisoned in a nerve gas attack likely came into contact with the deadly substance at his front door, British police revealed Wednesday.

That’s where detectives investigating the March 4 assault on Sergei Skripal and his daughter Yuliahave so far found the highest concentration of nerve agent, authorities say.

“At this point in our investigation, we believe the Skripals first came in contact with the nerve agent from their front door. We are therefore focusing much of our efforts in and around their address,” Deputy Assistant Commissioner Dean Haydon said in a statement

Police have also searched other sites around the city of Salisbury — including a pub, a restaurant and a cemetery — and found traces of the nerve agent in some spots, but at a lower concentration as on the front door of the former double agent’s house, he said.

Britain is blaming Russia for the attack, and has expelled a number of Russian diplomats from the UK as punishment — as have the US and other Western allies.

Russia denies any involvement.

The Skripals remain in the hospital, and a relative on Wednesday said she’s not hopeful they’ll make it.

“Out of 99 percent I have maybe 1 percent of hope. Whatever it was has given them a very small chance of survival. But they’re going to be invalids for the rest of their lives,” Sergei’s niece Viktoria Skripal told the BBC.