Blood samples taken from "a small number of people" feared to have been exposed to a nerve agent in Salisbury were negative, police have said.
The Metropolitan Police said:
Counter terrorism detectives can confirm that forensic tests carried out on blood samples, which were taken from a small number of people back in March 2018, have found no traces of Novichok.
The attempt to kill former Russian military officer Sergei Skripal in March2018 saw a total of six people exposed to Novichok.
Wiltshire Detective Sergeant Nick Bailey is also thought to have come into contact with the poison when he searched their home.
Three months later, Dawn Sturgess died after coming into contact with a perfume bottle believed to have been used in the attack on the Skripals.
Her partner, Charlie Rowley, was left seriously ill but later recovered.
Investigators found last month that a second Wiltshire officer, who did not wish to be named, also had traces of the nerve agent in his blood.
Two Russian men, Alexander Petrov and Ruslan Boshirov, are accused of carrying out the attack while they were in the UK in 2018.
The Metropolitan Police is continuing an appeal for information about theirwhereabouts.