There are no alarming signs with skull and crossbones evident at Plumas Eureka State Park.

Day trippers were still enjoying the historic buildings and picnic areas around the park headquarters.

Blue jays cruised looking for an easy meal and the fat trout beckoned from the creek, but up the road at the Upper Jamison Creek Campground the "closed' sign told it all.

Last night nearly half of the 70 campsites here were occupied. By noon today it was empty. A dead rodent had been found here and that rodent had tested positive for bubonic plague. The campground was closed.

The closure came as a surprise, and not a pleasant one, to visitors who had planned their vacation around a stay in this campground.

Those who were here were told to leave. Those who, like the Bui family from Sacramento, arrived expecting to find the campsite they had reserved months before were faced with a sudden change of plans.

"We've been planning this for three months," said Karen Bui.

Ranger Mike Rominger could only offer his regrets and a partial solution.

"What we're currently doing is honoring their reservations at another campground in the state park system."

Park staff found empty spots for this Sacramento family at Lake Tahoe for Thursday and Friday , but since most parks are fully booked on the weekend, their vacation may be cut short.

There's an abundance of caution being taken here. Most Sierra rodents have fleas and fleas can carry the plague, but although the disease is present throughout the Sierra, human cases are rare. The last reported here was more than 30 years ago.

Still, anytime a squirrel or chipmunk gets close to a person there's a danger and we've all seen that happen. Campers often coax the little rodents in closer, tempting them with food.

"People like squirrels and chipmunks because they're cute," says Rominger, "and they want to feed them, but they shouldn't.

That's good advice anywhere, any time in the Sierra.

Rominger says the campground will be treated and tested again next week. If they're successful, there's still hope it could reopen by the Labor Day weekend.

In the meantime, the rest of the park, all the day use areas, remains open.