Four people have been charged with various drug offences, including drug trafficking, as part of the Vancouver Police Department's 'Project Trapdoor.'

The VPD project began in August 2008 and focused on two marijuana transfer houses, one in the 3200-block of Renfrew Street and another in the 4800-block of Knight Street.

Police surveyed the residences for several months and witnessed more than 70 vehicles -- many of them known to be connected to the illegal drug trade -- visiting the locations to pick up and drop off various marijuana-related materials.

In Pictures: Project Trapdoor drug bust

In total, 38 pounds of marijuana, worth $120,000 in American and Canadian currency, several vehicles and one residence on Knight Street were seized.

A woman was arrested outside a home in the 2700-block of E. 16th Avenue, where she was seen passing a marijuana-filled black duffel bag to anther man, several feet from where her five-year-old child was waiting in her car.

The child and an older sibling are now in the care of the Ministry of Children and Family Development.

Transfer houses

The transfer houses are a part of larger commercial marijuana grow operations -- sometimes called factory grows -- which are "highly sophisticated grows that, in most cases, use the latest technology to boost the growing cycle," said Inspector Brad Desmarais of the VPD.

The sole focus of the houses is to create an easy stream of untaxed, lucrative income. The marijuana industry evolves with technology and organizers continue to find new ways and buildings in which to boost their income.

Police said the transfer houses are an integral part of the business and involve many people -- including the producers, stagers, dealers and buyers.