HONG KONG (AFP) - Hong Kong Customs officials have seized about 700kg of suspected crystal meth sent from Mexico, the authorities said on Sunday (April 10), the biggest haul of the drug in the city's history.

The methamphetamine was hidden inside two consignments of heavy industrial gear, said Mr Lee Kam Wing, head of the Customs department's drug investigation bureau.

The drug arrived in the city by air and sea within one week in March.

The equipment was arranged to ship from Mexico with a mainland Chinese logistics company, which was also asked to find a Hong Kong company to receive and store it, Mr Lee said.

"In that way, the drug dealers did not have to show up at all... it's very cunning," Mr Lee said.

Nearly 450kg of liquid meth was found in three transformers - each weighing 500kg - at the city's airport.

That led officers to 253kg of meth powder with a similar import pattern, which had been stowed inside shock absorption rubbers and had already been transported to a warehouse in a rural area near the mainland border.

Customs officers had to call in firefighters to saw their way into the equipment.

"The syndicate used such heavy industrial equipment with complicated structures that was difficult to open up for one single purpose - to avoid examination by Customs," Mr Lee said.

Two men working for local logistics companies handling the shipments were arrested and released on bail, as Mr Lee vowed to chase down the overseas syndicate in collaboration with the mainland authorities.

Hong Kong Customs have seized 1.2 tonnes of various drugs so far this year, 4.6 times more than in the same period last year.

Meth, the second most popular drug in Hong Kong, tops this year's seizure list with 814kg so far, an elevenfold increase on 71kg in the first quarter last year.