The final three suspects arrested in connection with the London Tube bombing attack have now been released without charge.

Scotland Yard said a 25-year-old man who was arrested in Newport, south Wales, on September 19, and a 30-year-old man arrested in Newport on September 20, were released yesterday.

A 20-year-old man arrested in Cardiff, Wales, on Monday, has also been released.

A total of seven men had been arrested as part of the investigation into the September 15 attack on the London Underground network in west London, being led by the Metropolitan Police’s Counter-Terrorism Command.

Of them, 18-year-old Ahmed Hassan has since been the only one officially named and charged.

He remains in judicial custody to appear before the Old Bailey court in London on October 13.

“To date, seven people have been arrested as part of the investigation being carried out by the Met’s Counter Terrorism Command. One person has been charged and the other six released with no further action,” a Met Police statement said.

The Met’s Counter-Terrorism Command says its investigation into the terror attack remains ongoing as it continues to search an address in Cardiff.

Searches near a home in Surrey have now been completed and the Met said that “work is currently underway to return the scene to normal”.

Police have revealed the explosive used by the prime suspect in the terror attack as triacetone triperoxide (TATP), similar to ingredients used in some of the previous terror attacks in Europe such as in Paris in November, 2015.

Thirty people were injured when a bomb partially exploded on a rush-hour Tube train in southwest London on September 15, leading to the UK briefly raising its terror threat level from ‘severe’ to ‘critical’   implying another attack was imminent.

The terror threat has since returned to severe, which indicates a terrorist attack remains highly likely.