From Michael Pearson and Dave Alsup, CNN
(CNN) - Search crews began scouring the vast backcountry of the Great Smoky Mountains National Park on Friday morning, hours after severe thunderstorms swept through east Tennessee, killing two people and injuring eight, park officials said.
An unknown number of hikers and campers may have weathered the Thursday night storm on the dozens of trails and backcountry camping sites in the most hard-hit portion of the park, park spokesman Carey Jones said Friday morning.
"We have no idea how many people are in the backcountry," he said. "We're just now getting people onto trails."
Hundreds, perhaps thousands, of people were visiting the nation's most-visited national park when the storms hit, Jones said.
Forty miles of roads in the park remained closed Friday due to downed trees, he said.
Park officials said late Thursday that one man had died in a motorcycle accident, while a woman was killed in a separate incident when a tree fell on her.
Park officials had confirmed eight other injuries, Jones said.
The area near Cades Cove, an isolated valley that offers some of the best wildlife viewing opportunities in the park, was one of the hardest hit by the storm, Jones said. The area, which is accessible by only one road, remained closed to visitors Friday.
The weather that hit the park began as a cluster of thunderstorms that formed along the Ohio River moving south. The storms continued to intensify as they got into more heat and humidity, and converged on the foothills of the Smokies.
Straight-line winds of 70 mph were recorded.
The storm hit during the busy Fourth of July week at the park, which straddles the Tennessee and North Carolina border.
The park covers more than 800 square miles in the Southern Appalachian Mountains and boasts a diversity of plants and animal life, and is known for its beauty.
Between 8 million and 10 million people visit the park each year, according to the National Park Service.
CNN's Rob Marciano and Mariano Castillo contributed to this report.
