Zahara Rahimzadegan, also known as Mandy Ahmadi, disappeared from her Ashwood home on December 16 and police hold grave fears for her safety.
Ms Rahimzadegan arrived in Australia as an Iranian refugee in 1999 and converted from the Muslim faith to Christianity.
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Until she went missing, the 46-year-old helped spread Christianity among other Muslim refugees in Melbourne's southeastern suburbs.
Her husband, and some of her associates, have been pushing the idea that Islamic radicals may have targeted her. "Maybe somebody kidnapped (her)," her husband told Network Ten.
"We don't like you, you're Christian and you convert the people to Christianity."
But on Thursday, the head of Victoria's homicide squad made it clear that detectives gave no weight to that particular theory.
"We've certainly looked at that particular allegation," Detective Inspector John Potter told reporters.
"We don't believe that suggestion has any foundation."
He said her husband, who reported her missing 48 hours after she disappeared, is not considered a suspect.
"We don't have other evidence to suggest foul play, but the circumstances of her going missing require us to take this case over," he said.
"She's now missing for nearly four weeks. Her handbag and her purse were discovered at home. The phone is missing and she's made no contact with any of her friends or family, which is highly out of character."
Police say she has disappeared before for a couple of days at a time due to issues at home, but has always contacted her children, two boys aged 15 and 11.
She has since missed Christmas and there's been no activity on her Facebook page, her phone or her bank accounts.
Detectives are speaking with anyone who had contact with her in the last days before she disappeared.
