Queensland's great flood for the first quarter of 2013 may have already went past, but the effects of the recent floods caused by ex-cyclone Oswald apparently are still not. On early Tuesday morning, a two-storey building that housed a marine supplies business caved in a "sinkhole" in flood-ravaged Bundaberg where authorities fear could further swallow at least 10 more other business establishments along its way.

"I came into work early, went down and took some photographs and it was already dropped into the water, but it was held up by a farm gate onto the front of the roller door for safety," Jan Douglas, owner of Midtown Marina, said of the cave-in that happened at 7:30am (AEST).

"You could hear the creaking and we saw it slowly just topple into the sinkhole."

Mal Forman, town mayor, said much of what's on the bank of the Burnett River was unstable following January's deluge.

He said at least 10 business establishments on Quay Street are at risk and may experience the same as that of Midtown Marina, especially since a 20-metre section of the river bank had collapsed from the rain last month.

"The way it's happened is very frightening to see it collapse so quickly and such a large area, but I think when you look down there's areas that could fall away as well," he told ABC.

David Crisafulli, Community Recovery and Resilience Minister, meanwhile, urged residents to not stop rebuilding their lives amid the latest setback.

''There's no doubt we should always keep a watching brief on the weather, but that does not mean that we should let it dent our spirits,'' he told reporters in Bundaberg.

''We have got to keep rebuilding this place. We cannot stop.''

Ms Douglas said she had just actually finished rebuilding from the 2011 floods when the latest January 2013 flooding disaster hit.

"We lost the complete marina last floods and spent every cent we had on it and it's like the last two years have been for nothing."