The British government is seeking an urgent meeting of the United Nations Security Council to update members about the attack on former double agent Sergei Skripal, RT reported.

Skripal and his daughter Yulia were found slumped on a bench in Salisbury on March 3. British authorities claim both were poisoned with a Soviet-engineered nerve agent called Novichok. Both remain in critical condition in hospital.

The Foreign Office tweeted Wednesday morning that the British government has called for an urgent UNSC meeting over the attack. Prime Minister Theresa May alleges that it was either authorized by the Russian government or Moscow allowed the nerve agent to fall into the wrong hands.

May set a deadline of midnight Tuesday for Russia to provide an explanation for the “poisoning” of Skripal and his daughter, and expelled 23 Russian diplomats when the deadline was missed. Speaking on Wednesday, Russian Foreign Minister Sergey Lavrov said Russia is ready to respond to to any official request from London but Moscow has yet to receive any such contact regarding the case. Moscow  denies any involvement in the incident.