Speaking to the media this morning, Queensland Premier Anna Bligh said there were still 72 people unnacounted for.
"We have whole families unnacounted for", Ms Bligh sai, adding there were 'grave fears' for many of the missing.
Earlier, Queensland's Disaster Co-ordinator, Ian Stewart, said nothing could have prepared authorities or local communities for the deadly surge that swept through Toowoomba and the Lockyer Valley west of Brisbane on Monday.
Mr Stewart, also a deputy police commissioner, said the toll was likely to rise above the eight deaths confirmed so far.
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"I personally believe it will get worse today, and we are waiting on confirmation from a number of concerning reports," Mr Stewart told the ABC.
"I can still only confirm eight deaths from this event (but) we are concerned about 72 other missing persons that we have reports on," he told the Nine Network.
"Obviously, our focus now, today, will be to try and help the survivors because we still have a large number of people isolated in the township of Grantham.
"There is actually bad weather right across Toowoomba and that part of the Lockyer Valley so we're actually being hampered in our efforts to get personnel in there to do a full and comprehensive search."
He said the valley community of Murphys Creek - where the bodies of a man and a boy were found on Monday - was of concern.
"It's quite a narrow ravine type area ... and we are waiting for confirmation of any further loss of life in that area," Mr Stewart said.
He said homes in Murphys Creek had been swept away and others had been severely damaged, with vehicles also swept off roads and dumped in creeks.
Withcott was also hit hard.
"We had three teenagers washed off a culvert and into a creek. We believe they have been accounted for now, but we also had cars washed off the Warrego Highway in that area," Mr Stewart said.
"So whilst we're confirming at the moment eight persons deceased, we're certainly very, very concerned about a range of other reports that are coming in."
Mr Stewart said the township of Grantham, between Withcott and Gatton, was among the hardest hit. Dozens of people remained stranded there on Tuesday.
"Grantham is going to be, in my view, just a disaster in terms of the number of homes that have been damaged or destroyed and we're waiting on confirmation of potential extra loss of life."
Earlier, Nine Network reporter Cameron Price, who is at Grantham, told the ABC the town had been devastated.
"The town is like a cyclone has gone through it," he said.
"There are houses that are completely collapsed, cars that are halfway up trees, homes a kilometre away from where they were."
To contact the SES in Queensland, call 132 500, and head to the Department of Main Roads for full road closures information.
