SALISBURY, England -- British police say two more people have been poisoned by the same type of nerve agent used to attack a Russian former spy and his daughter. The new victims were found in Amesbury, England, just a few miles from the scene of the alleged assassination attempt in March, and officials now believe they are likely secondary, unintended victims of that attack.

CBS News correspondent Charlie D'Agata is at the hospital in Salisbury, England, where the pair are being treated. British media have identified them as Charlie Rowley, 45, and Dawn Sturgess, 44.

Paramedics in hazmat suits stretchered them out of an apartment in Amesbury, about eight miles from Salisbury, on Saturday evening.

But it wasn't until Wednesday night that lab results confirmed the dreaded news, delivered by Scotland Yard, that "the man and woman have been exposed to the nerve agent Novichok."

It is the same type of nerve agent used in the attack on Russian double agent Sergei Skripal and his daughter Yulia that Britain blamed squarely on Russia.

Sam Hobson was with Rowley when he became violently ill on Saturday.

"He was rocking against the wall and his eyes were all red and pricked and he started sweating loads and dribbling, so I had to phone an ambulance for him," Hobson recalls.

British security officials said Thursday that they're working on the assumption the pair in Amesbury were not specifically targeted, but were instead victims of the previous attack.

Police tape now surrounds an entire park in Salisbury that the couple had visited. It is just a short walk from where the Skripals were found collapsed on a bench.

It is possible that the couple from Amesbury stumbled across a dangerous amount of the nerve agent, maybe on instruments used in that initial attack.

Unlike most chemical nerve agents, Novichok can remain deadly for long periods of time, according to chemical weapons expert Hamish de Bretton Gordon.

"Most nerve agents are not very persistent and last for days, possibly weeks," he tells CBS News. "We understand that Novichoks were designed to last for months, so four months down the line, is obviously still toxic."

And that presents a new and urgent challenge for counterterrorism police in England.