Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds.

LONDON, ENGLAND - SEPTEMBER 15:  A police officer stands next to a street sign near Parsons Green Underground Station on September 15, 2017 in London, England. Several people have been injured after an explosion on a tube train in south-west London. The Police are treating the incident as terrorism.  (Photo by Jack Taylor/Getty Images)
LONDON, ENGLAND - SEPTEMBER 15:  A police officer stands next to a street sign near Parsons Green Underground Station on September 15, 2017 in London, England. Several people have been injured after an explosion on a tube train in south-west London. The Police are treating the incident as terrorism.  (Photo by Jack Taylor/Getty Images)

    JUST WATCHED

    UK terror threat level raised to 'critical'

MUST WATCH

UK terror threat level raised to 'critical'

The London Underground station where an improvised device exploded on a train reopened as a huge manhunt for those responsible for the terrorist attack entered its second day. CNN's Brian Todd reports.

UK terror threat level raised to 'critical'

The London Underground station where an improvised device exploded on a train reopened as a huge manhunt for those responsible for the terrorist attack entered its second day. CNN's Brian Todd reports.