A source close to local police told Sputnik on Thursday that the woman had already been questioned and they now planned to speak with the man.
The victims were identified by UK media as UK national Alex King and his wife Anna Shapiro, an Israeli citizen of Russian origin. Police said the incident was not being treated as suspicious after the poisoning of Russian ex-spy Sergei Skripal and his daughter in March.
On Sunday night, a man and a woman suddenly felt sick at the Prezzo restaurant in downtown Salisbury. The British media speculated that "at least one" of the victims was Russian.