An intruder raped a woman after getting into her home by claiming to be a workman.
The attacker pretended to be a central heating engineer.
The man, who was wearing blue overalls and work boots, called at the house in Hartlepool on Wednesday afternoon and told the victim that her husband had asked him to repair the central heating.
She allowed him into the house where he threatened her, punched her in the face then carried out the rape.
After the man fled from the house in the Alwick Road and York Road area of the town, his 36-year-old victim called a friend for help and the police were alerted.
Detectives fear the man will attack again, and are appealing for his relatives or friends to come forward.
Detective Inspector Bob Bussey said: "Clearly this man poses a threat to other women and, if not caught, he may attack again.
"I would ask anyone who was in the area at 3pm on Wednesday, who may have seen the man, to get in touch, or anyone who suspects or believes they may know this man to come forward.
"I realise it may be asking someone to report a husband, son, boyfriend or relative, but he must be caught before he can commit another offence with perhaps more serious consequences."
DI Bussey has also urged people to be wary about letting strangers into their home without checking their identity.
He said: "I would appeal to householders to be very cautious when allowing people into their homes and to check identity very thoroughly before letting them in."
The rapist is described as in his early thirties, about 5ft 6in tall, chubby with a local accent.
He was unshaven with close-cropped black, straight hair, blue eyes and thick eyebrows.
Anyone with information about the attack is asked to call (01642) 302129
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