Police have arrested a man following the discovery of two bodies at the same rural property near Grafton in northern New South Wales, with investigators treating both deaths as suspicious.

The investigation began on September 13, when police were called to a property on Summerland Way at Gurranang, about 25 kilometres north of Grafton, after the body of a 79-year-old man was found inside the house.

Police established a crime scene and began investigating the circumstances surrounding the man's death.

On September 28, officers returned to the same property while conducting further inquiries into the original death. During that visit, they discovered the body of another man, believed to be aged 59.

The discovery prompted detectives from the State Crime Command's Homicide Squad to become involved in the investigation. Strike Force Faneel was established to examine the circumstances surrounding both deaths.

Police have said there are indications that foul play may have been involved. Investigators are examining the circumstances of both deaths and whether they are connected.

The second man was reportedly visiting the property and police believe he may have died within the previous 24 to 48 hours before his body was discovered. Police confirmed that the two deceased men were known to each other.

On September 29, detectives arrested a 32-year-old man at Grafton Base Hospital. Police said the man is believed to have lived in Gurranang.

Following his arrest, the man was taken to Grafton Police Station, where he remained in custody while detectives continued their investigation.

No charges had been laid against the man at the time of the ABC report. Police said investigators still had significant work to complete before establishing exactly what had occurred.

The property remains a crime scene and detectives are expected to continue examining the location for several days. Forensic investigations and inquiries into the movements and relationships of the people involved will form part of the investigation.

Police have not publicly established the relationship between the arrested man and the two deceased men. They have also not publicly confirmed a motive.

The deaths have resulted in a significant police operation involving local officers and homicide detectives. Investigators are working to determine how both men died and whether the circumstances surrounding the deaths are connected.

Authorities are urging anyone who may have information about the property, the people involved or events in the area to contact Crime Stoppers.

The investigation remains ongoing, and the arrest does not mean the 32-year-old man has been charged or found responsible for either death.