The camera was situated more than half a mile (1km) away from Plimsoll Way, looking towards the dock path where Sam was last seen, Ch Insp Stafford said.
“Our enquiries do remain ongoing, to continue to understand Sam’s movements and identify any additional information,” he added.
“Our underwater search unit remain out on the water and officers continue carrying out enquiries aided by information from the public.”
Officers searching for Sam have looked at hours of CCTV footage and carried out house-to-house inquiries.
His family have left care packages around the city, including food, water and a heartfelt note urging him to ask for help.
Police also appealed for two people who may have seen Sam to come forward.
Ch Insp Stafford said: “We continue to appeal to the two individuals seen in our CCTV appeal shared earlier in the week, as well as anyone else who has information that could assist us.
“I want to reiterate my thanks to members of the public for their assistance in the search for Sam, and to everyone who has come forward with information, your help has been invaluable to this search.”
