The disappearance of a mother in South Australia’s far north is being treated as suspicious.

Trisha Graf, 41, was last seen in the Roxby Downs area almost a month ago with her Ford Territory found abandoned east of Andamooka on the day she went missing.

South Australia Police have grave fears for her safety.

Trisha Graf, 41, was last seen in the Roxby Downs area almost a month ago with her Ford Territory found abandoned east of Andamooka on the day she went missing. (SA Police)

Graf had been with friends at the Roxby Downs hotel until at about 12.30am on Friday, December 12.

The pair hit a kangaroo on the way home a short distance from the Andamooka township.

After striking the kangaroo Trisha and her friend continued onto Andamooka where they visited a home in the north-western area of the town.

Trisha Graf left the pub with a friend in her white 2012 Ford Territory with the licence plate S254BCX and drove to a home in north-western Andamooka. (SA Police)

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At 2am Graf left to travel a short distance home and was last seen alive driving along Dunstan Drive.

Her car was found abandoned near Blue Dam just after midday.

“This is highly unusual and particularly out of character for her,” South Australia Police detective superintendent Darren Fielke said.

“The dam has been searched by police divers, polair has been involved in aerial searching and we’ve also utilised specialised drone equipment,” Fielke said.

“Police have spoken to a number of people and in Roxby Downs who have assisted piecing together the movements of Trisha.”

Detectives are now urging anyone who saw Graf in the hours before her disappearance on December 12 to contact them.