LONDON (AP) — The investigative group Bellingcat is reporting that one of the two suspects in the poisoning of an ex-spy in England is a doctor who works for Russian military intelligence.

Bellingcat said on its website Monday that the man British authorities identified as Alexander Petrov is actually Alexander Mishkin, a trained doctor working for the Russian military intelligence unit known as GRU.

The website claims Mishkin traveled from Russia to Salisbury, England, using Alexander Petrov as an alias. British officials said when they brought charges in the March nerve agent attack on Sergei Skripal and his daughter that they believed Petrov was an assumed name.

Bellingcat reported last month that the other suspect also traveled under an alias and was a decorated military agent named Anatoliy Chepiga.