Four people are in hospital after a mysterious incident at Woolworths in Mentone.

Emergency services initially responded to reports of a gas leak, which has since been ruled out, at the bakery in the supermarket.

Paramedics assessed a number of workers who said they were feeling ill, with a man and three women taken to hospital for observation.

Technicians have been called in to inspect the fridge in the bakery.

At this stage it appears one worker began to feel sick at the smell of fermenting dough, with the cause of the illness in the other workers believed to be psychosomatic.