A $1 million reward is being offered to help solve the two-decades-old murder of a mother as authorities desperately seek answers to crack the cold case.

Theresa Binge, 43, was reported missing days after disappearing from O'Shea's Royal Hotel in Goondiwindi, Queensland, on July 18, 2003.

Her body was found weeks later in a stormwater culvert beneath a rural road just across the border in NSW.

Police in the northern NSW town of Moree launched a murder investigation after the discovery but no charges have ever been laid over Ms Binge's death.

Detectives will travel to Moree on Tuesday to announce the $1 million reward alongside her daughter, Daylene Barlow.

The reward builds on a $100,000 offer announced in 2007 for information leading to an arrest and conviction for the crime.

A coro

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