Lincolnshire detectives said the woman's body was discovered by her daughter after she was released from hospital following her ordeal.
She had been dragged along a footpath and sexually assaulted after being accosted as she was walking near her home in Tetney just before 9am yesterday. Police who questioned her about the rape said she was in a "very distressed state".
Shortly after she left hospital to be with her family, the pensioner was found dead. A post-mortem examination was due to be carried out last night.
Police set up an incident room at Louth police station and are hunting her attacker, who is said to be aged between 30 and 40. Police described him as stout and said he was wearing a dark jumper and jeans.
When details of the rape were released earlier yesterday, a police spokesman said: "It is a very bad incident. I have not heard of anything like this before in my time in the police. That it should happen at that time in the morning to a woman in her 70s is incredible."
At this stage, the incident is not being treated as a murder until the cause of death has been established. Inspector Simon Craft said: "It's tragic. The lady had spoken to us about the incident and was very shaken up and distressed. She returned home to her family, but later she was found dead by her daughter." He added: "There would have been a lot of people about [at the time she was raped], and we are appealing for anyone who saw anything to contact us."Reuse content