Health officials in England on Sunday asked hundreds of people who visited a restaurant and a pub where a Russian spy may have been poisoned to wash their clothes. The advisory was for people who were at the Mill pub or Zizzi restaurant in the city of Salisbury on March 4 or March 5.

Last week, the police found the substance that rendered the spy critically ill on March 4 was a nerve agent. Sergei Skripal, a former Russian double agent, and his daughter Yulia were found unconscious on Sunday on a bench outside the Maltings shopping centre. Both of them, and a police officer who first responded to them, are said to be in serious condition in hospital.

Authorities said on Sunday they had found traces of the nerve agent in Mill pub and Zizzi restaurant, Reuters reported.

In its advisory, Public Health England said there was no immediate health risk to visitors to the restaurant or the pub, but it was possible that the poisonous substance might have come in contact with their clothing or belongings. The advisory said the health risk was low.

Public Health England also asked people to wipe phones, handbags or electronic items they may have carried to the two eateries, and to hand-wash jewellery or spectacles.

Toxic nerve agents enter the body through nose or mouth and attack the nervous system, subsequently stopping it from working.