Forensic police believe they have found the body of missing South Australian woman Jody Meyers under a newly laid concrete slab in a shed in her partner's parents' yard.

Detectives announced they discovered a body, just underneath the slab, a short time ago. The newly laid concrete slab is understood to be located in a shed at the rear of the Mannum property.

Officers have also blocked off the street and surrounding area as they search the property.

Detectives reached out to Ms Meyers' partner, Neil Archer, yesterday. After several exchanges the 29-year-old agreed to meet detectives at "an agreed upon location" about 1am, where he was arrested.

He was later taken to Murray Bridge Police Station and charged with the murder of his partner.

The 20-year-old deceased woman was last seen leaving a family barbecue on August 26 with Mr Archer.

"Following inquiries yesterday, police became concerned that Jody Meyers was potentially buried under concrete in a tool shed," South Australian Police's Detective Inspector Greg Hutchins said.

"The decision was made yesterday evening that police would return to excavate the site."

A police guard was left on the site overnight.

Mr Archer’s mother was charged yesterday with using Ms Meyers’ ATM card to withdraw money from the missing woman's account on the day after she disappeared.

She was later bailed to appear in the Murray Bridge Magistrates Court on September 30.

Det Insp Hutchins said detectives had continued to keep Ms Meyers' family informed throughout the investigation.

Ms Meyers has not been seen since August 26. (Supplied)

“One cannot have any degree of comprehension the level of pain and suffering that Jody’s family are going through," he said.

And the pain (they) have gone through over the past few weeks, not knowing."