Detectives say the 35-year-old's disappearance in southern Brisbane around January 16 or 17 is linked to the second man vanishing in the state's north on the same month.
Forensic analysts have made a breakthrough in the case on Monday after combing the premises of a private transport depot in Coopers Plains, which police raided on February 14.
Police are expected to hold a briefing on their investigation later on Monday afternoon.
Mr Griffiths, who's known to police, had been staying at the Meriton Hotel on Heschel St, in the Brisbane CBD, when he went missing.
It's believed he was taken by car with other people to the Coopers Plains depot, police say, where his "last signs of life" were recorded about January 16 or 17.
Mr Griffiths' mother, who's in regular contact with him, reported her son missing about 10 days later.
Detective Inspector David Jackman said last month that detectives had traced his movements down to the depot, which was full of industrial waste, but found no trace of Mr Griffiths there.
"We have no signs of life of that person post that date of the 16th or 17th of January, so we have got concerns for his current whereabouts; we are actually treating this as a homicide investigation," he told reporters on February 14.
Police seized the car that Mr Griffiths is believed to have been taken to the transport depot in, Det Insp Jackman said, and had spoke to a number of witnesses, including persons of interest.
"But at this stage, were still undergoing investigations into like I said: the circumstances, how he came to be at that address or around that address at the time," he said.
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