Bill Macpherson of the Regional District of Central Kootenay said the regional medical officer issued the order around 9 p.m. Friday for an area stretching several kilometres along both sides of the Lemon Creek in the Slocan Valley.
Emergency Management B.C. said on its website that all areas 10 kilometres downstream of the accident site to the community of Winlaw are included in the order.
A precautionary do not use order has also been issued to all users of water supplies within 10 km downstream of the accident site.
"The reason for the evacuation-order area being as broad as it is is strictly precautionary, but you always have to be concerned with jet fuel," said Macpherson.
"There are serious potential health concerns, especially with fumes in confined spaces and there's "always the potential of the explosiveness of the fumes."
Residents affected by the evacuation order are being asked to go to emergency centres set up in three area schools.
Macpherson said the order is mandatory, however, anyone over the age of 16 can refuse to leave if they so choose.
Bill Barisoff, who lives in Winlaw about half a block from the Slocan River, said he found out about the spill from a friend who phoned him just as he was heading to bed.
By 11 p.m. Friday, he said he hadn't been issued an evacuation order.
"No knock on the door. I live right by the fire hall. There was no action here whatsoever," he said. "My property adjoines the fire hall."
Resident John Boe said he lives on the river in downtown Winlaw and hadn't heard anything about the spill or evacuation order, but he knew something was wrong.
"It's a light smell, but I can smell it," he said, noting the scent was like diesel fuel.
"I don't see nothing else happening. Nobody's around here. So there's nobody coming to our door or anything yet."
Officials were informed of the accident along the Lemon Creek Forest Service Road, a gravel route, in the Slocan Valley at about 5:15 p.m.
The truck had been on its way to supply helicopters battling wildfires in the Perry Ridge area when the accident occurred.
"The RCMP were first responders and they were unable to get too close to the tanker itself because of fumes from jet fuel," said Macpherson.
There's no official word on the fate of the truck driver, or on the possible contamination of the creek, which feeds into the Slocan River.
Winlaw is a community of about 400 people in the Slocan Valley, 19 kilometres south of Slocan and 46 kilometres north of Castlegar.
According to the Ministry of Forests, the Perry Ridge fire is burning about 4.5 kilometres west of Winlaw and was discovered on Wednesday.
The ministry says 65 firefighters and five helicopters have been battling the blaze which is estimated to be about 35 hectares in size.
-- by Keven Drews in Vancouver