According to the SkyNews broadcaster, citing Western Ambulance Service, that the two people affected were conscious and were being provided with first medical assistance at the scene.
The wiltshire police said in a statement on Monday that an alleged nerve agent attack was not the case in the medical incident.
"Earlier this evening, Wiltshire Police and partners declared a major incident following a report that two people had fallen ill in Salisbury. Police received a call from the ambulance service to Prezzo restaurant, in High Street… Two people, a man aged in his 40s and a woman aged in her 30s, had become unwell," the police said in a statement.
The police indicated that it was not clear yet if a crime had been committed, adding that the investigation was ongoing.
Safety precautions have frequently been taken in Salisbury after the March events when former Russian militarty intelligence officer Sergei Skripal and his daughter Yulia were allegedly poisoned with what London claimed was the A234 nerve agent.