Police arrested an 18-year-old man Saturday, September 16 morning in the port area of Dover in connection with an attack a day earlier on a train at a London Underground station, London's Metropolitan Police said, according to CNN.

It was a "significant arrest" as the investigation continues, Deputy Assistant Commissioner Neil Basu, the senior national coordinator for counterterrorism policing, said in a statement.

"This arrest will lead to more activity from our officers. For strong investigative reasons, we will not give any more details on the man we arrested at this stage," he said.

The islamic State group has claimed involvement in the train blast but has offered no evidence to support the claim.

Dover, about 80 miles southeast of London, is a port town with regular ferry services to France.

The suspect, who was arrested under the Terrorism Act, was being held in a local police station, the Met Police said. He will be transferred to a south London police station "in due course," the statement said.

The station in Parsons Green, southwest London, where an improvised device exploded as a train stopped during the Friday morning rush hour, reopened early Saturday -- with a visible police presence as doors first opened.

Meanwhile, hundreds of police officers scoured CCTV footage, questioned dozens of witnesses and studied the remnants of the device in search of clues to the identity of those responsible.