Danielle Lee Fels, 40, missing from Kippa-Ring

A missing Brisbane woman was once charged with murdering two siblings in what police alleged was a case of mistaken identity.

Danielle Fels is missing from Kippa-Ring

A woman missing from Kippa-Ring was once charged with murdering two siblings before the case was discontinued.

Danielle Lee Fels, 40, was last seen on Anzac Ave about 11pm on February 17 but has not been seen since.

Police say they are concerned for her welfare because she has a medical condition which requires treatment.

Ms Fels was previously charged with the murder of siblings April Bailey, 29 and her brother Ian Bailey, 31.

The pair were found inside their burnt out Deception Bay home in May 2004.

Investigators believe up to four unknown people killed the pair.

April and Ian Bailey were found dead in their Deception Bay home in 2004 after it was destroyed by fire.

Detectives have previously said they believe the siblings were killed in a horrific case of mistaken identity.

Investigators believe the people got the “wrong April” and had meant to target another woman called April who they believed had a large amount of drugs.

Ms Fels pleaded not guilty in the Supreme Court in Brisbane.

The prosecution later announced they would not proceed with the case, with the charges dropped.

In an appeal on Monday investigators asked the public to contact police if they see Ms Fels.

“Danielle is described as caucasian in appearance, approximately 160cm tall with a proportionate build, brown eyes, dark brown hair and a distinctive tattoo above her eyebrow,” police said in a statement.

“Extensive investigations have so far failed to locate Danielle.

“Police urge Danielle, or anyone with information regarding her whereabouts, to immediately call police.”