A Russian law enforcement committee is requesting Britain provide legal assistance in the case of the poisoning of Yulia Skirpal.
She and her father, former Russian double agent Sergei Skirpal, fell ill earlier this month after being poisoned with a nerve toxin in the British town of Salisbury. They remain in critical condition.
The Russian committee is asking British investigators to take a number of steps aimed at determining the circumstances of the poisoning and to provide copies of certain material from the probe.
British officials have blamed Russia for the attack, saying it involved the nerve agent Novichok that was first developed by the Soviet military.
Russia denies it was responsible and has alleged the attack was carried out by British intelligence services in order to make Russia look bad. Britain dismisses that allegation.
British police gave an update on the investigation Wednesday, saying that after forensic examinations detectives believe the Skirpals first made contact with the toxin at the front door of their home. They cautioned that those living in the neighborhood will see continued searches taking place but that the risk to the public remains low.
So far, police say they have looked through 5,000 security camera videos, examined more than 1,350 other exhibits and interviewed hundreds of witnesses.
In a phone call with U.S. President Donald Trump, British Prime Minister Theresa May praised the "very strong response" by the United States, which ordered the expulsion of 60 Russian diplomats after Moscow was blamed for the attack.
The White House said "both leaders agreed on the importance of dismantling Russia’s spy networks in the United Kingdom and the United States to curtail Russian clandestine activities and prevent future chemical weapons attacks on either country’s soil."
More than 20 other nations have joined the U.S. in ordering the expulsions of Russian diplomats. May said she welcomes "the breadth of international action in response to Russia's reckless and brazen behavior."
Russia has denied any involvement in the attack.
Russian Foreign Minister Sergey Lavrov said Moscow would respond to the U.S.-led moves within a week. He described the expulsion of his countries' diplomats from Western countries as "boorish anti-Russian behavior" and said colossal blackmail "is now, unfortunately, the main tool of Washington on the international arena."
Russia's Ambassador to Australia Grigory Logvinov added Wednesday that if Western countries continue actions against Russia, then the world would be "deeply in a Cold War situation."
VOA's Jeff Seldin and Steve Herman contributed to this report.