A helicopter bucketing water to a wildfire blazing in B.C.'s southern Interior crashed Thursday afternoon, sending its occupants to hospital.

Two people were on board when the Bell 214-B chopper, carrying a full load of water, hit the side of a large hill while fighting the Jade Wildfire burning northwest of Lillooet, about two hours west of Kamloops.

Both were found conscious. The 61-year-old pilot was taken to Royal Inland Hospital in Kamloops with a concussion and leg injury, while his 27-year-old co-pilot was treated for minor bumps and bruises and released in Lillooet.

The helicopter was on contract to the B.C. Fire Service by TransWest Helicopters, based in Chilliwack.

It is still not known what caused the crash.

In Pictures: Yakalom Valley fire

The Yalakom Valley fire, sparked by lightning July 21, is now 10 square kilometres in size and is only 15-per-cent contained.

On Wednesday, fire officials said crews were limited to fighting the blaze from the air because it is on such steep terrain.

A total of 125 firefighters, five structure protection unit personnel, 11 helicopters and 12 pieces of heavy equipment are working to contain the wildfire.

High winds were forecast for the region Thursday.