Three men have been charged after Australian Federal Police intercepted 500kg of cocaine off a boat ramp in central Queensland.

The AFP said officers had been monitoring the men – aged 27, 45 and 66 – who had driven from NSW to Gladstone, Queensland in April.The men allegedly travelled in an 8.2-metre fishing boat to an offshore cargo ship to collect the half tonne haul late on Sunday night.

Police intercepted the men when they returned to the Boyne Island boat ramp, 24km south of Gladstone.

Officers found 15 black and yellow waterproof bags which contained 32 blocks weighing 1kg each of a powdered substance that tested positive for cocaine.

“It was a very large seizure, one of the largest in Queensland,” AFP Commander John Tanti told reporters on Tuesday.

“The alleged attempt to collect cocaine from the ocean shows the extreme lengths criminals will go to in order to attempt to bring illicit drugs into Australia.”

The seizure was worth about $162 million if sold on the streets, the AFP said.

It is believed the cargo ship had come from South America, likely from a Peru port.

Police are investigating where the cocaine was destined to go but Mr Tanti said it would have supplied the national drug trade.

Australian Border Force Commander Jim Ley said identifying the eight-metre fishing boat was like finding a needle in a haystack.

“Looking for one eight-metre vessel in the whole coast of Queensland is a massive effort but that is a testament to the combined capabilities of Australian law enforcement,” he said.

The Gladstone port is watched closely by law enforcement given the number of large-scale imports that enter it, Mr Ley said.

The three men, who were known to police, have been charged with possessing a commercial quantity of an unlawfully imported border-controlled drug.

It carries a maximum sentence of life in prison.

The trio will face Gladstone Magistrates Court on July 19.

It comes weeks after two men were charged by police over two unrelated cocaine importation plots in Queensland.

A Victorian man has been charged over his alleged involvement in a criminal syndicate that imported 289kg of cocaine.

And a Queensland man has been charged after being accused of trying to import two tonnes of cocaine worth $683 million over the past year.

Mr Tanti said Queensland is not being targeted as a drug marketplace however criminal enterprises are landing on the state’s shores.

“These people employ quite a bit of ingenuity trying to land drugs across the whole of the country,” he said.

“They’ll use whatever port and diversify that to hit the Australian marketplace.”