Dawn Sturgess, a 44-year-old British woman who was exposed to a nerve agent novichok, died on Sunday in hospital, reported the New York Times.
Sturgess and her partner were exposed to Novichok in England's Amesbury. Her partner Charlie Rowley's condition still remains critical.
Novichok was one of a strain of nerve agents that are said to be kept under the tight control of the Russian authorities.
Following the incident, the British authorities have now opened a murder investigation.
As per the police, Sturgess, most likely exposed accidentally to residue from a Soviet-developed, military-grade nerve agent used on the former spy, Sergei V. Skripal in a March attack.
The investigation into the matter is being led by detectives from the Counter Terrorism Policing Network and the investigators are still trying to determine how the couple were exposed to the substance.
Following the incident, Britain has accused Russia of sending the poison to a small city in England in an attempt to kill a former spy.
Though, Russia has denied any involvement in the issue.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)