Police are to begin searching for the body of Clapham attack suspect Abdul Shokoor Ezedi in the River Thames.
Detectives believe the 35-year-old went into the water near Chelsea Bridge in west London on the night of the attack, after walking "with purpose" for hours.
The search of the Thames will involve boats from the Marine Policing Unit - and will take place at low tide.
In CCTV footage, the suspect is seen pacing and leaning over the railings before disappearing from view.
Ezedi has not been seen since the night of the attack on 31 January, when an alkali substance was thrown over a mother and her two children.
The last sighting was at 23:27 GMT, on Chelsea Bridge, about four hours after the attack in Clapham, south London. He was never seen leaving the bridge area.
Scotland Yard warned that at this time of year the Thames was very fast flowing and full of snags, and that it was possible his body wouldn't appear for up to a month or never actually surface.
Speaking at Scotland Yard on Friday, Cmdr Jon Savell said officers had spent the last 24 hours "meticulously" following CCTV and their "main working hypothesis" was that he had gone into the water.
"We have looked at all of the available cameras and angles, and with the assistance of Transport for London and CCTV from buses that were travelling over the bridge at the relevant time and there is no sighting of him coming off the bridge," he said,
Cmdr Savell said that a marine support unit would be "carrying out some searches of the Thames" in the area was last seen.
He said the fast flow of the river at this time of year meant it "may be some time... for a person to surface - and sadly, they may never actually be found."
He added that police were in contact with a member of Ezedi's family to "break that news".
Detective Superintendent Rick Sewart said death was the "most probable outcome" if Ezedi had gone into the water.
Police said Ezedi's death was the most probable outcome only days after saying they believed he was "being helped by others" to hide, and that their inquiries were targeting "more of Ezedi's associates" following the arrest of one man on suspicion of assisting an offender.
Searches had been ongoing for more than a week, with police raids carried out in the Newcastle area at properties linked to Ezedi on Thursday.
He is wanted on suspicion of attempted murder over the attack, which took place in Lesser Avenue at about 19:25.
The woman, who police said had been in a relationship with the suspect, remains sedated in hospital and there are concerns she may lose sight in one eye. Both children, aged eight and three, have been discharged.
Police said their thoughts remained with the mother, who was still "very poorly and unable to speak to police".
The suspect, who is not the father of the children, suffered serious facial injuries in the incident which police had said could be fatal.
Ezedi is an Afghan refugee who came to the UK in a lorry in 2016.
He had his asylum claim rejected twice before he successfully appealed against the Home Office by claiming he had converted to Christianity.
Ezedi was also convicted of two sexual offences in 2018 but was allowed to stay because his crimes did not meet the threshold for deportation.