Detectives have been granted more time to question two men held over the Parsons Green terror attack.
The men, aged 18 and 21, were arrested on Saturday over the bombing on a London Tube train during Friday morning rush hour.
The 21-year-old has been identified by his employers as Yahyah Farroukh, but the identity of the other man has yet to be released.
The suspects are understood to be from Iraq and Syria and are thought to have been fostered by the same British couple.
Scotland Yard said magistrates had granted warrants allowing the 18-year-old to be held until Saturday September 23, and Farroukh until Thursday September 21.
The news came as CCTV footage that appears to show the bomb suspect on his way to plant his homemade device was discovered.
The video, obtained exclusively by ITV News, shows a figure dressed in grey carrying a distinctive white Lidl carrier bag leaving the Sunbury-on-Thames home of the respected foster couple.
Ninety minutes later the bucket bomb went off at Parsons Green Tube station injuring 30 people.
Both Farroukh and the 18-year-old, understood to be the suspected bomber, are believed to have spent time in foster care with Penelope and Ronald Jones, aged 71 and 88 respectively, who previously received MBEs for services to 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.
The younger suspect was detained on Saturday morning in the departure area of Dover ferry port, the busiest ferry hub in Europe and a gateway to the French coast.