VICTORIA, B.C. - The operators of a mushroom farm near Vancouver where three workers were killed and two were brain injured in September 2008 when they were overcome by toxic fumes were charged Monday with a series of offences under British Columbia's labour laws.

Crown counsel announced a total of 29 charges under the Workers Compensation Act and Occupational Health and Safety Regulations against A-1 Mushroom Substratum Ltd., H.V. Truong Ltd. and four people who are either officers or directors of those companies. Those four individuals are Ha Qua Troung, Vy Tri Trong, Van Thi Truong and Thinh Huu Doan.

Those charges include failing to ensure the health and safety of workers, failing to fix hazardous conditions, failing to ensure workers are aware of the safety hazards they face, inadequate training, and failing to create an adequate safety plan.

On Sept. 5, 2008, a group of workers at a mushroom farm and composting plant in Langley were overcome by toxic fumes in a shed, setting off what WorkSafe BC has said was one of the most complex investigations the agency has ever conducted.

Three people died and two suffered severe neurological injuries. One of the injured survivors is still in a coma, and the other is left unable to speak or hear. All were Vietnamese-Canadians.

Investigators have said a pipe carrying a compost mixture broke, releasing the gas.

Fellow workers rushed to the aid of two men who initially succumbed to the fumes in the shed. One of those would-be rescuers also died, and two others were taken to hospital.

Tracey Phan, whose father Michael Phan is still in a coma, noted the maximum sentence for the charges is six months in jail.

"I'm happy that the (charges) were given out, but I don't think six months is enough," Phan said in an interview after appearing at a news conference organized by the Opposition NDP.

"The three men that passed away, I don't think six months will do justice for them."

Nga Trieu, whose husband Hang Pham died at the farm, said through a translator that the provincial government needs to strengthen its laws to ensure farmworkers are safe.

"She would like to call upon the government to monitor the policy to force the owner or the company to make sure that there are safety procedures in the workplace so similar accidents will not happen," said Que-Tran Hoang, who works for provincial NDP politician and translated for family members. "When it happens, it is too late."

The NDP's labour critic said the province needs to call a public inquiry into the safety of farmworkers.

"The government has not taken enough steps to prevent these deaths and injuries in the workplace," said Raj Chouhan.

The New Democrats, the B.C. Federation of Labour and the victim's families have called for changes to the province's agriculture industry, where many workers are migrants from countries such as Mexico or Vietnam who have limited English skills.

The federation has said the work site offered a pamphlet on working in confined spaces,but it was available only in English.

They've called for changes including language training, a more rigorous inspection and enforcement system, improved training and revisions to employment rules to ensure farmworkers are covered by the same standards and have the same rights as everyone else.

Chouhan noted the leak at the Langley mushroom farm isn't the only case in recent years involving the deaths of farmworkers in B.C.

Three farmworkers were killed in March 2007 when a 15-passenger van carrying 17 people flipped onto a concrete median on the Trans-Canada Highway near Abbotsford.

A coroner's jury ruled the death accidental, but made 18 recommendations, including ensuring farmworkers are better informed about their rights.