As prosecutors declared the largest opium bust in Canadian history to be much larger than first estimated, two men charged in connection with the 2010 Chilliwack poppy grow entered surprise guilty pleas Monday.

Tehal Singh Bath, of Abbotsford, and Mandeep Singh Dhaliwal, of Mission, each entered guilty pleas to charges of production of a controlled substance and possession for the purpose of trafficking.

The two men were arrested Aug. 23, 2010, when police raided a Sardis field. At the time, Mounties said they found 60,000 opium plants. (The opium is believed to have been destined for use in the manufacture of doda, a powder that, when combined with tea or hot water, provides a quick high and sense of well-being.)

A four-day trial expected to begin Monday was aborted when Bath and Dhaliwal entered guilty pleas.

But with few legal precedents to draw upon and the number of plants likely to be contested, Crown counsel Brad Smith decided to call witnesses to speak to the details of the operation.

Smith said the number of plants might be more than nine times higher than first estimated.

"The best estimate is that there were some 560,000 plants," he told the court.

Smith also said Bath and Dhaliwal "were present when the lease, or a document purporting to be a lease, was signed."

Police have said the owner of the land, a retiree who has owned the property since 1969, knew nothing about the opium field.

When Mounties first came across the parcel of land, they too didn't know whether they were looking at opium plants.

The Crown's first witness, Chilliwack RCMP drug investigator Cpl. Kurtis Bosnell, took the stand Monday morning. He told the court police had begun staking out the seven-acre peanut-shaped property, at 41894 Keith Wilson Rd., on July 6, 2010, after receiving a tip from the public.

Officers used a telephoto lens to take photos of the plants from a neighbouring property. The photos were then sent to an expert in Calgary who said they were opium plants. That was enough for police to obtain a "general warrant." On Aug. 21, under the cover of darkness, Mounties surreptitiously picked eight plants from the property. The plants, which had matured considerably since police first started investigating in early July, tested positive for opium. That gave police enough evidence to obtain a search warrant and execute the full-scale raid two days later.

Police raided the field on Aug. 23, 2010, arresting both Dhaliwal and Bath. They also seized a black minivan, which Bosnell said had been seen at the field multiple times and was registered in Dhaliwal's name.

The sentencing hearing will continue on Thursday, with more submissions expected at a later date.

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