The Bellingcat investigative website on Monday said the second suspect in the poisoning of former Russian spy Sergei Skripal is Dr Alexander Mishkin, a military doctor working for Russian intelligence agency GRU.

Sergei Skripal and his daughter Yulia Skripal became critically ill after being exposed to a nerve agent in March. They were found unconscious on a bench outside the Maltings shopping centre in Salisbury. The British government has blamed Russia for the attack.

The website said it discovered Mishkin’s real identity after obtaining a scanned copy of his passport. Mishkin had travelled to the United Kingdom under the name of Alexander Petrov.

“Bellingcat’s identification process included multiple open sources, testimony from people familiar with the person, as well as copies of personally identifying documents, including a scanned copy of his passport,” the website said. “The identification process will be described in the upcoming full report.” The website said it would publish the report on Tuesday.

The website claimed Mishkin travelled extensively from 2011 to 2018 on a fake identity. He graduated from the Military Medical Academy in Russia and was probably a colonel or lieutenant colonel when Skripal and his daughter were poisoned.

The website had earlier identified Ruslan Boshirov, the first suspect, as the GRU’s Anatoliy Chepiga. Moscow has rejected the accusation.