Police have formally ended the search for three‑month‑old Lewis Wright, with specialist divers unable to locate the missing infant in treacherous waters off South Australia.

SA Police confirmed the marine operation was wound down on July 29 after crews spent days battling dangerous surf, poor visibility and powerful swells along the Cape Northumberland coastline.

WATCH ABOVE: Deaths of Lewis, Hazel and their mother Helena Wright ruled murder-suicide by police

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Last week, however, specialist divers returned to the rocky coast to try and locate the missing three-month-old.

Sadly, his body remains missing.

The search for missing infant Lewis Wright has concluded. Credit: Gofundme/SAPOL

Police Commissioner Grant Stevens said on Tuesday the search had taken a heavy toll on those involved.

“This is a really difficult investigation and search effort for those involved,” he said.

“We have had our divers down late last week, conducting further search activity.

“We’ll be making assessments as to what further search activity is undertaken.”

The search for Lewis Wright has been made difficult by the terrain on the coast Credit: 7NEWS

Limestone Coast superintendent Trent Cox said that while the formal search had ended, police would still respond to any future reports.

“It doesn’t mean that from time to time we won’t get called to investigate something that may have washed up,” he told the ABC.

“But for now there’s no formal search effort underway.”

Police previously said the environment remained “extremely hazardous”, with underwater terrain and strong surges making the search the fall “not survivable” for such a young child.

Lewis disappeared on July 27 in what detectives have classified as a murder‑suicide, after his mother Helena Wright and his sister Hazel were found dead in the water at the base of a cliff.

Police do not believe they fell from the cliff accidentally.

The coronial investigation remains ongoing and police say there is no evidence anyone else was involved.