The 30-year-old model and her 42-year-old husband reportedly were hospitalized after having dinner in the city, which already hit the headlines in March with the poisoning of former Russian agent Sergei Skripal and his daughter Yulia.
The incident on Sunday was revealed by British tabloid The Sun, which reported that senior security sources believed the pair may have been attacked with the rat poison strychnine.
While Shapiro has been discharged and is currently staying at a Salisbury hotel under 24/7 police surveillance, her husband Kind is still in the hospital in critical condition.
"It is harrowing waiting for news of Alex. I feel lucky but the doctors are not sure about him. He has regained consciousness which is marvelous. But we're still waiting for his test results. I'm so scared and wanted to leave London as I didn't feel safe. Now this has happened," Shapiro told The Sun.
The Russian-born part-time model reportedly became an Israeli citizen in 2006 despite heavy opposition from her family and later moved to London in 2008. Shapiro and King got married last month.
Shapiro, whose father was a general in the Russian army, believes that she became a target after publicly criticizing Russian President Vladimir Putin. The model even claimed that the Russian intelligence considered her a "spy."
"I was targeted by Putin's henchmen. They want me dead as I oppose Putin and have turned my back on my country. Russia is capable of anything," she told The Sun.
Whiltshire Police said Tuesday that tests confirmed Shapiro and King "were not exposed to any kind of nerve agent."
Security officers wearing bio-hazard suits had evacuated nearby restaurants and bars following the poisoning incident.
Tensions between Britain and Russia rose after Prime Minister Theresa May accused Kremlin of being behind the nerve agent attack on the Skripals, which Russia has since denied.
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