Police in Woodstock are continuing their search for 57-year-old Brenda Duncan, who has been missing since Tuesday morning.

Due to the lack of evidence, police say they are still unable to rule out foul play in the case, and their concern grows as more time passes.

However, they can confirm that her credit cards, bank accounts and cell phone have not been used since she disappeared, and she was not carrying much cash or her passport.

An air search around Woodstock and as far as Port Rowan on Thursday did not turn up any additional information.

The one unexplained element of the case is that Duncan called in sick to her job as a social worker just before her disappearance, despite reportedly leaving for work as usual.

Police are asking anyone with information or who may have seen her red Mazda 5 van, licence plate BCSJ 791, to contact them at 519-537-2323 or local police.