Police patrol on a street in London, Britain on Sept. 17, 2017. (Xinhua/Stephen Chung)
British police questioned two suspects on Monday -- an 18-year-old Iraqi refugee who is believed to have planted a homemade explosive device on a packed rush-hour subway carriage in west London on Friday, and a 21-year-old from Syria, who is named by police as Yahyah Farroukh.
They were both arrested on Saturday in connection with the Friday explosion at a Tube train at Parsons Green subway station in west London, which left 30 people injured.
Forensic tents are still being erected in the gardens of a terrace house in Stanwell, Surrey, some 26 km from central London, where the two suspects are believed to have spent time being fostered by Penelope and Ronald Jones, aged 71 and 88, who were known for fostering hundreds of children, including war zone refugees.
The country's threat level was downgraded from critical to severe on Sunday night shortly after a second arrest was made in west London meaning a terrorist attack is highly possible.
Britain had been warned that a terrorist attack could be "imminent" after the bomb suspect fled the scene and went on the run.
However, the reduction of the terror threat suggests that Scotland Yard believes the person who planted the homemade bomb on the subway train was not part of a wider terror network.
However, British detectives will now be seeking to establish if those responsible had traveled to Britain as genuine refugees, or if they were actually members of the Islamic State of Iraq and the Levant (ISIS), who had been sent to specifically carry out an attack.
The 18-year-old was arrested by chance when two unarmed police officers spotted him at the Port of Dover. At that time, he was trying to buy a ferry ticket to flee the country.
Hours after his arrest, which London police described as "significant", the second suspect was arrested at a chicken shop in Hounslow, west London.
According to Farroukh's own Facebook page, he had moved to London from the Syrian capital of Damascus.
He fled the Syrian civil war in 2013, going first to Egypt and then Italy, reports said.
London police began to search the home of a second refuge foster child on Sunday night as part of the terror probe following the Friday blast, caused by the explosive device which partially detonated.
The Parsons Green attack was the fifth terrorist attack in the country in the past six months.
Previous attacks in London this year at Westminster Bridge, London Bridge and Finsbury Park as well as a blast at an Ariana Grande concert in Manchester killed dozens of people and injured more than 150.
Both men remain in custody under section 41 of the Terrorism Act 2000, which allows police to detain suspects without charge beyond the four days allowed for suspects connected to other crimes.
The possibility that the two became friends overseas is being actively investigated.
