SYDNEY, April 8 (Xinhua) -- Over half a tonne of the drug methylamphetamine, also known as ice, with an estimated 310 million U.S. dollar street value has been seized by border authorities in Sydney.

The Australian Border Force (ABF) said on Monday that 585 kg of the drug was concealed within 11 commercial refrigerators being shipped into the country.

"We've had such an effect on the smaller, scattergun-type imports and now they appear to be going for broke with bigger ones and we're finding those," ABF Superintendent Garry Low said.

"As much as they may try and change their methodology, we'll change our targeting and we'll find them."

A joint investigation has been launched by the ABF, Australian Federal Police and New South Wales Police Force's Organized Crime Squad.

On Friday officers executed search warrants at two properties in Sydney, seizing documents and electronic storage devices.