Police have seized 766 kilograms of MDMA powder, in the third-largest seizure of the drug in Australian history and the largest seizure of the drug in Queensland.

The powder could have made 6 million-12 million ecstasy tablets, with an estimated street value of at least $90 million.

The batch was uncovered as part of an international investigation into a Britain-based organised-crime syndicate.

Queensland police searched two Loganlea properties, south of Brisbane, while officers in NSW raided three residences across Lennox Head and Ballina.