Police confirmed a report of the TV station ATV, which suggested that the bucket also contained human body parts.
They are suspected to have come from a 54-year-old millionaire bank customer from Graz, who was allegedly killed by his two advisors when he discovered their alleged embezzlement of his funds.
Information came from one of the perpetrators, describing where to find the body parts. The 23-year-old suspect claims that his was only a passive role in the crime.
His 29-year-old accomplice denied involvement at the first hearing, and has remained silent ever since.
Other containers that match the descriptions of the suspect were spotted in the river. The recovery of three further concrete buckets is underway, police commander Andreas Dirnberger told the APA.
Due to the strong currents in the river, divers must proceed very carefully.
"The tubs are as described," said Dirnberger. The site is located just north of Frohnleiten, in the surrounding districts of Graz.