Three people have died and three became seriously ill after being overcome by fumes of an undetermined nature in a pump house at a mushroom farm south of Vancouver.

Two remained at a hospital Sunday, two days after the episode at Farmers Fresh Mushrooms Inc. in Langley, roughly half a dozen miles north of Blaine, Wash.

Police identified one of the victims as Ut Tran, 35, of Surrey. Thirty-five-year-old Michael Phan of Langley was listed in serious condition and there was no word on the condition of the other person who was hospitalized.

Owner Ha Quan Truong has been unavailable for comment.

The Workers Compensation Board of British Columbia, known as WorkeSafeBC, has been trying to determine the nature of the fumes and how they escaped.

"We're still making the site safe," said John Eldridge, the agency's manager of fatal and serious injury investigations. "We can't really go in and take a look inside this pump house yet because it's still not a safe environment for our investigators."

The British Columbia Federation of Labor has proposed a public inquiry and federation President Jim Sinclair said not enough has been done to protect the rights of immigrant workers.

He said he went to the farm and spoke to workers, most of them Vietnamese.

"We have a systemic problem of using a lot of immigrants to do the work who aren't necessarily trained to do the job," Sinclair said. "We need to look deeper into what's going on in this industry."

Neighbors say they have complained to authorities for years about a foul stench of manure.

"The smell can be at any time ... 10 minutes or four hours," said Roger Layton of the neighborhood group Citizens for Responsible Composting. "It depends which way the wind is blowing."

Huge piles of manure sit at the farm for weeks and composting is done at all hours, Layton said.

"They'd have a tractor out there and that tractor would mix it and a couple of guys would hose water on it and it would steam away and the wind would blow my way and you'd have to hide in the house," he said.

Another neighbor, Charlie Fox, a member of the municipal council, filed a complaint with the Farm Industry Review Board in June to have the farm inspected.

"When it's smelly, you can't have a barbecue because it's just uncomfortable," Fox said.