MOSCOW — Russia’s foreign minister says Moscow has received a document from a Swiss lab that analyzed the samples in the nerve agent poisoning of an ex-Russian spy, which points at a Western-designed nerve agent as a likely cause.

Minister Sergey Lavrov said Saturday that Moscow received the confidential information from the laboratory in Spiez, Switzerland, that analyzed samples from the site of the March 4 poisoning of Sergei Skripal and his daughter in the English city of Salisbury.

He said the analysis was done at the request of the Organization for the Prohibition of Chemical Weapons.

The OPCW’s report confirmed British findings that the Skripals were poisoned with a military-grade nerve agent, but didn’t say who was responsible.

Britain has accused Russia of poisoning them with a Soviet-designed agent, an accusation that Moscow denies.

Lavrov said the document indicated that the samples from Salisbury contained BZ nerve agent and its precursor. He said BZ was part of chemical arsenals of the U.S., Britain and other NATO countries, while the Soviet Union and Russia never developed the agent.

Lavrov added that the Swiss lab also pointed at the presence of the nerve agent A234 in the samples, but added that the lab noted that its presence in the samples appeared strange, given the substance’s high volatility and the relatively long period between the poisoning and the sample-taking.

He noted that OPCW’s report didn’t contain any mention of BZ, adding that Russia will ask the chemical weapons watchdog for an explanation.

Britain said that the A234 agent belonged to the family of Soviet-designed nerve agents dubbed Novichok.

Yulia Skripal, 33, was released from the hospital this week. Her father remains hospitalized but British health officials say he is improving.