The bus, with the registration number GT 5313-19, was reportedly travelling with passengers from Accra to Wulensi in the Northern region.
The GNA reports that the bus fell into the river while trying to get onto the pontoon to cross to the other side.
There were no casualties, while all the personal effects of passengers were also duly retrieved from the sinking bus.
One of the passenger on the bus, Obed Kagbetor, said the driver was attempting to park on the pontoon but the bus ended up steering into the river.
He told the GNA that he suspected the problem to be brake failure. Meanwhile, a Winch tractor was later brought to pull out the bus.
The Motor Traffic and Transport Division (MTTD), however, refused to comment on the incident.