British authorities say they have arrested an 18-year-old male in Dover in connection with Friday’s London subway attack. The suspect’s identity has not been revealed but Deputy Assistant Police Commissioner Neil Basu said Saturday it’s a “significant arrest” in the investigation. “Although we are pleased with the progress made, this investigation continues and the threat level remains at critical,” Basu said. Police also raided a home near London on Saturday afternoon as part of their ongoing investigation. Twenty-nine people were wounded in the blast at Parsons Green station during morning rush hour on Friday. Investigators say many likely would have been killed if the bomb had fully detonated rather than only partially exploding. The arrest comes after Prime Minister Theresa May announced that the country’s threat level is now at “critical,” with British soldiers to be deployed throughout the country to assist police in patrolling public areas.