More than 500 kilos of methamphetamine concealed in steel beams, have been found by authorities

Customs and police staff descended on a rural Waikato property in darkness, early on Friday morning.

Two men had been in the process of deconstructing the beams - they were arrested, along with three other men.

Customs initially located the concealed importation last month, after it was sent from the US.

Its estimated the shipment would've produced around 25-million individual doses of the drug.

Customs spokesman Terry Brown, says the method and scale of the smuggling operation, show the effort organised crime groups are willing to go to.