COCHRANE, Alta. -- A wildlife spokesman says a grizzly bear was trying to protect her cubs when she attacked two people at a campground in the backcountry northwest of Calgary.

A 25-year-old woman who was having a picnic with her boyfriend was charged and bitten on the arm by the mother grizzly on Tuesday.

Fish and wildlife spokesman Brendan Cox says the bear will not be tracked down and destroyed.

Coleman Blair, whose family owns the Trapper's Hill campground by the Ghost River, said he came upon the attack and was able to pry the bear's jaws open.

The woman was taken to hospital and was in stable condition.

Cox says a large part of the area will be closed to recreational use until further notice.

"The sow was reacting naturally to protect her cubs," Cox said Wednesday. "The cubs stumbled upon the pair. It reacted to defend them, so the bears will be left alone and given the space they need to move on on their own."

He said wildlife officers will monitor the region.

"The area will be opened again when officers are confident that it's safe to do that," Cox said.

"After a situation like this, it's typical that (the bears) will leave the immediate area quickly, but it is best practice to close off a larger area to help prevent similar incidents like this. We really can't put a timeline on how long it's going to be closed right now."

Warning signs and tape will advise hikers of the closure, Cox said.