SAN FRANCISCO (AP) — The mysterious deaths of a Northern California family of hikers and their dog have led federal officials to close 28 miles along the Merced River. The closure on Friday came after test results of water samples downstream from where the family died showed high levels of toxic algae. The Bureau of Land Management says the algae blooms can make people and pets extremely sick, so it closed access to campgrounds and recreation along the river as a precaution. The family and dog were found dead last month after a family friend reported them missing. A cause of death has not been determined. Investigators are considering whether toxic algae blooms or other hazards may have contributed to the deaths.