London, Sep 20 (IANS): Two more men were arrested on Wednesday over last week's terror attack on a London Tube train, taking the total number of suspects held to five, officials said.

A 48-year-old man and a 30-year-old man were detained under the Terrorism Act in the early hours after a search at an address in Newport, south Wales. Their identities and nationalities were not made available by the Scotland Yard, BBC reported.

Thirty people were injured when an improvised explosive device camouflaged inside a paint bucket partially detonated on a London Underground train at Parsons Green station on Friday.

"This continues to be a fast-moving investigation," said Commander Dean Haydon, head of the Metropolitan Police's counter-terror force. "Detectives are carrying out extensive inquiries to determine the full facts behind the attack."

Another man was arrested late Tuesday night in Newport, where police raided several homes. On Saturday, an 18-year-old was arrested at Dover port and a 21-year-old was arrested in Hounslow, an area near Heathrow airport.

Police also carried out raids on homes in Surrey, a county just outside southwest London, and Hounslow.

Shortly after the bombing, the UK raised the terror threat level to "critical" in response, but lowered it back to its second highest level on Sunday, meaning an attack was highly likely but not imminent.