A man in New South Wales is speaking with police following the discovery of a body in the riverside Brisbane suburb of Hamilton.

The body, which 9News.com.au understands was in a box, was found on Monday afternoon at an apartment complex on Parkside Circuit.

It's understood police were looking for a missing person before the discovery. They are treating the death as suspicious

"A crime scene has been declared at Hamilton following the discovery of a body this afternoon," Queensland Police said in a statement.

"Police had cause to attend the address, an apartment complex on Parkside Circuit shortly before 4pm."

Queensland Police said a 26-year-old man in NSW was assisting detectives with their inquiries.

The investigation is being run out of Hendra police station, down the road from where the body was found.