UPDATED, 4.02pm: The decayed remains of a body found at Tumbulgum on Saturday night are of a man between 50 and 70 years, police say.
Police said detectives from Tweed/Byron Local Area Command, with the assistance of the State Crime Command's Homicide Squad, are continuing investigations into the matter.
They are appealing to anyone who may have witnessed suspicious activity in the area to contact them.
Anyone with information about the matter is asked to contact Tweed Heads Police or Crime Stoppers on 1800 333 000. Information can be provided anonymously and will be dealt with in the strictest confidence.
INITIAL REPORT, 1.32pm: Police hope the gender and age of a body found in the Tweed River will be determined today.
A police spokeswoman said a post mortem examination would determine critical pieces of information about the remains found in a bag at Tumbulgum on Saturday.
"It is unknown if the body is male or female," she said.
The investigation is still at a local level with Tweed/Byron Local Area Command detectives and homicide investigating.
About 7pm on Saturday a Tumbulgum fisherman discovered a bag on the banks of the river near Dulguigan Rd.
He contacted police who visited the scene and confirmed the bag contained heavily decomposed human remains.
A police spokeswoman said the remains were not found in a plastic bag.
Tweed SES crews were tasked by police to search the Tweed River after a body was found.
Tweed regional SES controller Brian Sheahan said his members conducted a thorough land and boat search.
No evidence was found during the hour search which was conducted between Tumbulgum and Murwillumbah.
Tweed, Pottsville and Murwillumbah SES crews were all involved in the search.