Two children were found locked in a hot car after writing a 'help' message on the window to attract passers-by.
A six-year-old boy and a girl, ten, wrote the message in condensation that had formed on the window after spending an hour in the car, which had been deadlocked.
Concerned shoppers called the fire brigade but the male driver of the car, believed to be a family member, returned to the car in Rochdale and unlocked it before emergency services intervened.
Police and paramedics were called after the children complained of feeling unwell.
They were treated at the scene and taken to Rochdale Infirmary and the man was arrested on suspicion of child neglect.
Social services are now investigating the matter.
Witness Diane Leach saw the drama unfolding at 4.25pm last Friday.
She said: 'The car was locked and the children had been left inside and had written 'help' in the window.
'The fire brigade and police were called but a man came back with the keys before they had chance to smash into the car to get them out.
'It is believed that he said he would be gone 10 minutes but he was gone for about an hour. The children had overheated and I think they were suffering from dehydration. They were taken away in an ambulance.'
A police spokesman said: 'Police were called by the fire service to Yorkshire Street following reports a six-year old boy and a 10-year-old girl had been left in a car.
'They were taken to hospital as a precaution but released a short time later.'
A 20-year-old man was arrested on suspicion of child neglect and was released on bail until July 1 pending further inquiries.
A council spokesman said: 'We are aware of the incident and the details have been forwarded to children's social care for consideration.'
A spokesman for the NSPCC warned against leaving children alone inside cars.
He said: 'The NSPCC's advice on leaving children alone in cars is to always keep your child with you, wherever possible.
'If you decide it's safe to leave your child in the car always keep them within your sight and never leave them for more than a couple of minutes. Never leave a young child in the car if you can possibly avoid doing so.
'Always keep the car well ventilated, always keep children fastened in their car seats, never leave the key in the car or the doors unlocked, always park safely and legally and never expect young children to look after baby brothers and sisters.'
Source: Daily Mail