Editor's note: This updates with word that park officials believe everyone has been accounted for, reopening of Foothills Parkway West, forecast of more thunderstorms.

A thunderstorm packing winds gusting to 70 mph tore through Great Smoky Mountains National Park, downing hundreds of trees, killing two visitors, and injuring several others.

By early afternoon Friday officials believed everyone was accounted for, though some roads and campgrounds in the western portion of the park remained closed due to scores of downed trees. While some media reports mentioned missing hikers, Great Smoky spokeswoman Melissa Cobern said park officials believed everyone had been located.

"We were able to complete a sweep of every single road in the storm-damaged areas and some trails in that immediate area and made sure that everybody was out and accounted for," she said early Friday afternoon from her office. "I feel that by now, if something had happened in the backcountry, we would have heard about it by now."

The potent storm, which National Weather Service meteorologists had been tracking since the Fourth of July as it moved southeast through the United States, tore into the Smokies about 6 p.m. Eastern on Thursday. Behind it was a trail of downed trees and power lines. As it moved through the park, it showered trees down on visitors, including a group cooling off in a popular Abrams Creek swimming hole.

Killed by the storm was a Georgia man who was knocked off his motorcyle by a falling tree limb and a Tennessee woman hit by a tree in that swimming hole. The storm left a trail of damage from Metcalf Bottoms through Cades Cove and up to Abrams Creek.

Park officials say Ralph Frazier, 50, of Buford, Georgia, was hit in the head by the limb while driving about a half-mile east of the Townsend Wye in the park and died at the scene, while Rachael Burkhart, 41, of Corryton, Tennessee, was hit at the swimming hole near the Abrams Creek Campground and died at the scene. An unidentified passenger on Mr. Frazier's motorcycle was not injured.

The tree that killed Ms. Burkhart also hit a family of three that was in the water. A 7-year-old girl was knocked unconscious; bystanders pulled her from the water and performed CPR, said Ms. Cobern. The girl's father sustained fractured vertebrae, broken ribs, and a collapsed lung, while her mother suffered less serious injuries, the park spokeswoman added.

The girl and her father were airlifted to medical facilities at the University of Tennessee in Knoxville, while her mother was taken there by ground transportation. Ms. Cobern did not have updated conditions on any of the three.

“We are deeply saddened by the deaths of two of our visitors,” said Superintendent Dale Ditmanson.” Our thoughts are with their families and with those who were injured.”

Park Service crews were making good progress in clearing storm-damaged areas; however, hundreds of trees remain down in the west end of the park from Metcalf Bottoms to Abrams Creek, the park reported Friday afternoon. No other damage or injuries have been reported from any other areas of the park.

Although power has been restored to the Cades Cove area, Cades Cove facilities, as well as the Abrams Creek Campground remain closed. Roads into and out of those areas also remain closed. Crews are doing as much as feasible to expedite road clearing and to reopen roads in storm-damaged areas as soon as possible.

Officials have closed the Cades Cove Campground at least until Sunday evening, and the Lookrock Campground also was closed, as was the Little River Road from Elkmont to the Townsend Wye, the Laurel Creek Road, the Foothills Parkway West, the Cades Cove Loop Road, the Rich Mountain Road, Parson's Branch Road, Weir Gap Road, and Tremont Road. The Foothills Parkway was reopened later Friday once it had been cleared of storm debris.

There was no immediate word on structural damage in the park.

“We haven’t even had an opportunity to do a proper structural assessment at this time. We’ve been so busy getting roads cleared and makeing sure everybody is safe and getting medical atention to people who need it," Ms. Cobern said, adding that she hadn't "heard anything in regard to any buidlings or facilities.”

At the NWS office in Morristown, Tennessee, meteorologist Derek Eisentrout said staff had been tracking the storm since the Fourth of July.

“It was an organized area of thunderstorms that we had actually been following for over a day. On the Fourth of July it was up in the Minnesota area," he said, adding that by Thursday morning it had moved down over Ohio and headed on towards Tennessee.

“As it progressed further south, those thunderstorms just blossoomed as they hit our area," he said.

The storms carried a pool of cooler air in the upper levels of the atmosphere, and "when that hit the hot, humid air mass that we had here it caused pretty rapid convection, which caused pretty strong thunderstorms," the meteorologist explained.

While more thunderstorms were in the park's forecast for Friday afternoon and evening, Mr. Eisentrout said they weren't expected to be as powerful as the one that hit the park Thursday.

"You could get some severe storms, but nothing like yesterday," he said. "That was really an organized convective complex. This today is just going to be your summertime afternoon showers and thunderstorms.”

Powerful summer thunderstorms are not atypical for the Smokies. According to Weather Service records, "in 2008, 5 consecutive days of storms hit the area, resulting in extensive wind damage."