By Kate Holton
LONDON (Reuters) – Police arrested an 18-year-old man in the departure lounge of the port of Dover on Saturday in what they said was a “very significant” step in the hunt for whoever planted a bomb on a London commuter train that injured 30 people a day earlier.
Prime Minister Theresa May put Britain on the highest security level of “critical” late on Friday, meaning another attack may be imminent, and deployed soldiers and armed police to strategic locations such as nuclear power plants.
On Saturday morning officers in Dover, a ferry port on the southeast coast from which passenger ships sail to France, arrested a man and then partially evacuated the area, recovering a number of items, the police said without elaborating.
Hours later, police raided a house in a commuter town southwest of London, and evacuated nearby premises as a precaution. Police officers in forensic suits were seen entering a modest house in a suburban street in Sunbury, around 11 miles (18 km) from Parsons Green where the bomb exploded.
The police said they were keeping an open mind as to whether more than one person was involved in the Friday morning attack on a packed train in west London.
“We are still pursuing numerous lines of enquiry, and at great pace,” Senior National Co-ordinator for Counter Terrorism Policing Neil Basu told reporters.
“We’re open-minded. If there are other people responsible it’s our job to find them and that is part of the reason why we are remaining at ‘critical’ at the moment.”
Officials said the attack could have been deadly. The home-made bomb shot flames through a packed train carriage but apparently failed to detonate fully.
According to media reports, the device was attached to a timer, unlike other recent blasts which have typically been suicide bombs.
Pictures showed a slightly charred white plastic bucket with wires coming out of the top in a supermarket shopping bag on the floor of a train carriage.
“This is a very significant arrest,” said interior minister Amber Rudd of the 18-year-old. “The police have made very good progress but the operation is ongoing,” she said.
“There is no doubt that this was a serious IED (improvised explosive device) and it was good fortune that it did so little damage.”
Islamic State claimed responsibility. The group has claimed other attacks in Britain this year, including two in London and one at a concert by American singer Ariana Grande in Manchester, but intelligence officials say there is scant evidence…