Who Are Sergei And Yulia Skripal? Former Russian Spy, Daughter Allegedly Poisoned

United Kingdom’s counter-terrorism police have been helping with investigation into the suspected poisoning of former Russian double agent Sergei Skripal, the country's leading counter-terror officer Mark Rowley said Monday.

Sergei Skripal, 66, and another woman in her 30s, identified as his daughter Yulia Skripal, were found unconscious on a shopping center bench in Salisbury on Sunday. Authorities said they might have been exposed to an "unknown substance," and added they were investigating suspected poisoning.

Yulia was discovered next to Sergei, also on a bench, and is in a critical condition in hospital. Wiltshire, U.K, police said the two, found at The Maltings Shopping Centre in Salisbury, had no visible injuries on their bodies. However, officers were investigating whether a crime was committed.

The former Russian double agent's daughter resides in Russia, but was visiting the U.K., the BBC reported, adding relatives had not heard from her for two consecutive days.

“It’s a very unusual case and the critical thing is to get to the bottom of what’s caused these illnesses as quickly as possible,” Rowley, the Metropolitan Police assistant commissioner, told BBC. “If necessary we will bring that investigation into the counter-terrorism network. We’re doing all the things you would expect us to do, we’re speaking to witnesses, we’re taking forensic samples at the scene, we’re doing toxicology work and that will help us to get to an answer. I can’t say any more at this stage.”

The Kremlin, meanwhile, said it has "no information" on what could have caused the ex-agent convicted of spying for Britain to collapse in Salisbury during the weekend.

Russia said it was willing to co-operate in the police investigation.

Dmitry Peskov, Russian President Vladimir Putin's spokesman, told reporters Moscow was prepared to help with the investigation into the incident.

"We see this tragic situation but we don't have information on what could have led to this, what he was engaged in," he added.

Sergei and his daughter were taken to Salisbury district hospital. Public Health England radiation and toxicology experts have been called in to help with the investigation.

Two police officers dealing with the incident were also admitted to the hospital, BBC reported. They were reportedly suffering minor symptoms that could occur from poisoning, such as itchy eyes and wheezing.

Sergei, a former Russian army colonel, was convicted of passing the identities of Moscow agents working undercover in Europe to MI6 in the year 2006.

He was sentenced to 13 years in prison for spying for Britain in Russia in August 2006 after he was convicted of "high treason in the form of espionage." The Kremlin claimed he was paid $100,000 extracting classified information and state secrets. Sergei pleaded guilty during his trial. However, he was one of the four prisoners Russia swapped in 2010 for U.S. spies and was flown to the U.K.

Temporary Assistant Chief Constable Craig Holden in U.K. said regarding the pair: "They are currently being treated for suspected exposure to an unknown substance."

He added the police and multiple other agencies were involved in the investigation and they were keeping an "open mind." Meanwhile, authorities were said to have closed the nearby Zizzi restaurant "as a precaution." However, they stated there is no known risk to the wider public.