Jewellery store owner injected during robbery in Melbourne's west

A Melbourne store owner was injected with a substance that rendered him unconscious during a robbery, police say.

The 63-year-old man woke several hours after his Footscray jewellery store had been robbed of cash and jewellery.

Police have arrested a 38-year-old Ardeer woman and are interviewing her.

They say she may have dropped one of the stolen bags as she ran from the store about 5.30pm yesterday.