More than a dozen foreign nationals are facing charges over one of Western Australia's biggest drug seizures, linked to a suspicious boat that was intercepted off Geraldton in the Mid West.

It comes after 216kg of crystal methamphetamine was seized from two properties in suburban Perth — the equivalent of two million individual hits on the streets with a value of around $200 million, according to police.

The boat was inspected for several days after being escorted into Geraldton. ( ABC News: Chris Lewis )

WA Police deputy commissioner Gary Dreibergs said 14 people, eight Chinese nationals and six Malay nationals, would be charged over "the biggest methamphetamine seizure in WA this year".

It is alleged the Chinese nationals, aged between 37 and 56, used the fishing trawler to transport the drugs from China to WA, before using a runabout to drop them on a remote part of the coast four weeks ago.

Police said further investigations led them to raid homes across Perth and arrest six Malaysian men, aged between 24 and 54.

More than 150kg of methamphetamines was seized from a house in East Cannington, and a further 50kg from a house in Embleton.

Deputy commissioner Dreibergs said the syndicate had continued to operate in Perth despite knowing police had swooped on the trawler and impounded it.

"They certainly are brazen and they certainly are committed," he said.

"It is evident that this seizure is part of a well-funded, highly-organised, sophisticated overseas criminal organisation.

"Without the outstanding joint work of all Australian law enforcement agencies, this result would not have been achieved."

Haul follows long-running investigation

The investigation into the alleged drug smuggling operation started when the trawler was intercepted about 185 kilometres off the coast earlier this month and escorted to the Geraldton Fishermen's Wharf, 400 kilometres north of Perth.

Firefighters donned protective gear to remove items from the boat. ( ABC Open: Chris Lewis )

The vessel was inspected for several days as firefighters wearing protective gear removed containers suspected to have been used to hold chemicals.

Eight Chinese crew were later taken into immigration detention by the Australian Federal Police (AFP) as they "did not have valid visas to enter Australia".

The operation involved officers from WA Police, the AFP and Australian Border Force.

AFP commissioner David Stewart could not say if any of those arrested were key players in the alleged syndicate.

"We'll certainly allege that we have disrupted and dismantled a significant organised crime network," he said.

"It's very sophisticated because there are different elements of that group that we will be alleging participated in the importation of these narcotics."

Police said two of the men arrested over the haul were in WA on tourist visas.

The details of the case and those charged had been the subject of strict suppression orders issued by the Perth Magistrates Court in closed hearings over the past few days.