Walkers found the packs, each weighing a kilogram, on a beach at Ramsay Bay, Hinchinbrook Island, on Sunday.
Forensic analysis is being conducted on the powder, which police believe is cocaine.
Acting Senior Sergeant Graham Camp says more packages could wash up in the area in coming days.
“We urge the public to contact police should they find further packages and to not open them as the substance could be hazardous,” he said in a statement on Thursday.
Police are trying to work out where the packages came from and who owns them.
They have called for anyone with any information to contact them.
“Anyone who was at sea or on the coastline near these locations and saw anything suspicious in the water or other suspicious activity is urged to contact police,” Camp said.
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