Detectives were last night granted more time to question two young men held in raids over the Parsons Green terror attack.
An 18-year-old man and a 21-year-old, identified by his employers as Yahyah Farroukh, were arrested on Saturday over Friday morning's bomb attack on a London Underground train.
Scotland Yard said last night that magistrates had granted warrants allowing the 18-year-old to be held until Saturday, September 23, and Farroukh until Thursday, September 21.
The men, who are understood to be from Iraq and Syria respectively, are believed to have both been fostered by the same British couple.
The news came as fresh CCTV footage was discovered that appears to show the Parsons Green bomb suspect on his way to plant his homemade device.
The video shows a figure dressed in grey carrying a distinctive white Lidl carrier bag around 80 minutes before the explosion that injured 29 people.
The footage was obtained from a camera outside Ecco La Vera pizzeria in Vicarage Road in Sunbury-on-Thames.
Both Farroukh and the 18-year-old man are believed to have spent time in foster care with Penelope and Ronald Jones, aged 71 and 88 respectively, who previously received MBEs for their work with children and families.
A Scotland Yard spokesman said: "They both remain in custody at a south London police station.
"Searches are continuing at two addresses in Surrey and a commercial property in Hounslow in connection with this ongoing investigation."
Farroukh was arrested after he finished his shift at a fried chicken shop in Hounslow, west London.
Video obtained by The Sun appeared to show forensic officers gathering evidence as he was held against the shutters of the neighbouring pharmacy.
According to his Facebook profile, Farroukh is originally from Damascus and living in London, having studied English at West Thames College.
Suleman Sarwar (43), who owns Aladdin's Fried Chicken in Kingsley Road, Hounslow, with his brothers, said "very normal" Farroukh worked at the takeaway and was arrested outside the shop after his shift at around 11.30pm.
He continued: "It was at that point that the police all grabbed him."