U.K. Counter-Terror Specialists Offer Help After Former Russian Spy Collapses

British counter-terror specialists offered expertise to police in southern England Tuesday as they sought to unravel the mystery of why a former Russian spy fell critically ill following exposure to an "unknown substance."

Sergei Skripal during a court hearing in Moscow in 2006.

Photographer: TASS via Getty Images
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Salisbury, England (AP) -- Britain's counterterrorism police took over an investigation Tuesday into the mysterious collapse of a former spy and his daughter, now fighting for their lives. The government pledged a "robust" response if suspicions of Russian state involvement are proven.

Foreign Secretary Boris Johnson said he wasn't yet accusing anyone of harming Sergei Skripal and his daughter, Yulia. The two Russians collapsed Sunday on a bench in southern England after coming into contact with an unknown substance.