MOSCOW (Reuters) - Inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) conducted an inspection at an undisclosed location in Russia in the past week, the Russian Defence Ministry’s official newspaper said on Friday.

It was not clear if the inspection was linked to the nerve agent poisoning in Britain of former Russian double agent Sergei Skripal and his daughter, Yulia, or if it was routine.

A diplomatic source who spoke on condition of anonymity because of OPCW confidentiality rules said it was unlikely the visit was linked to the Salisbury case.

“It must have been related to a regular inspection” of a chemical industry site, the source said.

The OPCW, headquartered in The Hague, has been involved in the Skripal investigation and an English court last month gave its experts permission to test blood samples taken from the Skripals. OPCW inspectors are also looking into the toxin used in the attack.

The samples are being tested at independent, designated laboratories, which are expected to deliver their findings confidentially to the OPCW next week. The watchdog will not identify a culprit, but will confirm whether or not a banned chemical weapon was used.

The scientific findings will first be provided to the British delegation, which has said it will share them with the OPCW’s 41 executive council members, including the United States and Russia.

The Russian Defence Ministry’s official newspaper, Krasnaya Zvezda (Red Star), on Friday published a graphic showing events over the past week which included a mention of a visit to Russia by an “inspection group of the Technical Secretariat of the OPCW.”

It provided no further details.

Russia completed the destruction of roughly 40,000 tonnes of chemical weapons it declared to the OPCW last year. A visit might also have been a routine follow-up to the verification process.

Britain has said that the Russian state was “highly likely” to blame for the poisoning of Skripal and his daughter. British officials say they were poisoned using the “Novichok” nerve agent which, they say, was developed in the Soviet Union.

Moscow denies any involvement in the attack and says it has no stocks of “Novichok” or any other chemical weapon. A diplomatic row has flared up over the case, with scores of diplomats expelled in several countries.