The Melbourne man arrested after the disappearance of his partner has been released without charge.
Ju "Kelly" Zhang, a 33-year-old mother, has not been seen since leaving her home at Epping in Melbourne's outer north on February 1.
A friend reported her missing to police the next day.
Ms Zhang was in a relationship with Doncaster man Joon Seong Tan, 35, who was arrested on Sunday after allegedly trying to avoid police since Thursday.
He was interviewed by missing persons squad detectives on Sunday but later released without charge pending further enquiries.
"He's provided us with a version of an account of his last sighting of Kelly," Detective Inspector Andrew Stamper told reporters on Saturday.
"He has told us she went out for a walk and didn't come back.
"We say that is a very unlikely scenario bearing in mind that her eight-year-old son was in the house.
"The information we have is she would not have left him by himself with someone that wasn't a family member."
In light of Mr Tan's release from custody, police renewed their call for the public to help find the young mother.
"Detectives are keen to speak to anyone who may have seen Ju or has further information about her current whereabouts," a police spokeswoman said in a statement on Monday.
Ms Zhang was wearing a pink pyjama top, shorts and no shoes when she disappeared.
All of her family lives in China and her former husband, the child's father, is looking after their boy.
Foul play is an active line of inquiry for police.
"We do hold grave concerns for her welfare," Det Insp Stamper said.