Cobram Sen-Constable Mary-Jane Kane said a Cobram mother in her late 20s left her two daughters, aged five and 18 months, in the car while she went shopping at 12.30pm.

"The younger one was distressed and hot, the older one seemed to be quite mature, but certainly concerned when they were suddenly surrounded by the ambos, firies and police," Sen-Constable Kane said.

She said the children were left alone for about 10 minutes in the Woolworths carpark and either an employee or shopper reported it to emergency services.

Sen-Constable Kane said the car was left running with the air-conditioning on, not that it mattered in the eyes of the law.

"It is an offence to leave children unattended in a car in Victoria and particularly on a hot day like today," she said.

Investigations are continuing.