Under a declared statewide emergency, South Dakota military units and other road crews reopened Interstate 90 in the West River area Friday night.

The state Department of Public Safety and State Radio Communications said the state's main east-west highway reopened about 7:30 p.m. However, portions of I-90 remained slippery and snow-packed, state officials warned.

Meanwhile, many secondary roads remained blocked and drivers "are encouraged to use good judgment and cautioned to travel with care," a state Department of Public Safety news release said.

In nine counties, the good judgment call would follow the no-travel advisories. At 10 p.m., Butte, Harding and Perkins counties in the state's northwest corner, Lawrence, Meade, and Pennington counties in the Black Hills, and Bennett, Jackson and Jones in south and central sections still had closed roads, according to the release.

Although weather warmed and skies cleared, travel remained treacherous if not stopped Friday in many areas in the wake of this week's blizzard.

Snowplows were digging out U.S. Highway 212 between Newell and Faith, and crews were hoping for more resources to rescue as many as 50 people stranded on the isolated stretch of two-lane highway.

Travel on the highway between Belle Fourche and Newell was limited to emergency traffic. Butte County dispatch center chief Dallas Ford told one caller shortly after noon to not even think about travel in the area. "We're not going to be able to send anybody to get you if you go."

A medical emergency on the Pine Ridge Indian Reservation required a National Guard Blackhawk helicopter medical crew to carried four civilians, three requiring dialysis, from Wanblee to the Pine Ridge Hospital.

A Crazy Horse School employee said 150 to 200 people were stranded at school, 36 miles from Kyle, some since Wednesday night. Don Doyle said after appeals to tribal, federal and nonprofit officials, food supplies and patience were running out.

"We're just frustrated with people in leadership positions who say they can't help us," he said Friday night.

Officials said help was on the way, as soon as roads could be opened.

Gov. Mike Rounds and state emergency management officials toured the storm-struck region aboard another National Guard helicopter Friday afternoon, assessing the damage.

Rounds declared a state emergency due to the storm, which dumped nearly four feet of snow in the Deadwood area and knocked down power lines and stranded motorists throughout West River.

Twelve-foot drifts and dozens of stranded cars and trucks made clearing I-90 a nightmare. During the day, crews had opened the highway from the Wyoming border to Spearfish, between Exit 55 at Rapid City and Exit 67 at Box Elder, and from Murdo to Mitchell.

The state Highway Patrol at 4:30 p.m. said it would ticket motorists illegally entering the closed areas of the interstate.

State Department of Transportation spokesman Jason Humphries said earlier predictions of opening the interstate by Friday afternoon had been ambitious. State crews found conditions worse than anticipated; the large drifts and numerous stuck vehicles slowed expected progress.

State personnel on Friday continued to rescue stranded travelers and remove unattended vehicles abandoned along the interstate. State National Guard wreckers and snowplows were dispatched from Sioux Falls to work on the eastern end of the storm area, while Guard snowblowers from Rapid City were clearing I-90 toward Sturgis.

In Rapid City, a shelter set up by the Black Hills Chapter of the American Red Cross in Rapid City for stranded travelers and people with special needs who lost power went unused during the day Friday.

Director Richard Smith said local Red Cross crews today will begin assessing how to move supplies and volunteers to needed areas, focusing on Shannon and Ziebach counties. The emergency response efforts will depend on roads being safe.

Smith said the Red Cross was on hold like everyone else, waiting for roads to be cleared so resources can be moved to those in need.

The Rapid City fire department reported some "fairly significant problems overall with the weather" that caused long response times for medical units - sometime several hours - on Thursday.

Slower response times were a combination of poor visibility and road access because of snow removal, according to Mark Kirchgesler.

Rapid City Regional Airport was back in business by 11:15 a.m. Friday.

Cameron Humphres, airport executive director, said it was a long 36 hours for him and the airport maintenance staff who worked all night to remove two to three inches of hard ice and large snowdrifts on the runway.

The airport experienced frequent power outages, around three to four per hour during the height of the storm, due to the high winds from late Wednesday night through Thursday. Humphres said back-up generators operate critical lighting and computer systems at the airport, and the airfield is equipped with emergency generators.

Humphres said the only wind damage came when a rotating beacon was blown off its pole. Four hunters, a dog and a trucker were the only non-airport personnel stranded at the airport overnight.

"This was a worse storm than the one we had in May. We had sustained winds over 60 miles an hour and gusting winds approaching 80 miles an hour," he said. "It was close to 36 hours of those kinds of speed. We had incredible drifting out here."

Telephone service for MidContinent customers appeared close to being restored as of late Friday afternoon. About 1,000 customers lost telephone service during the storm when a fiber optic line was cut between Sturgis and Spearfish. The outage affected about 500 customers in the Rapid City and Box Elder area and about 500 in the Sturgis, Boulder Canyon and Whitewood areas.

Tom Simmons, senior vice president of public policy for MidContinent, said crews had located the damaged line and hoped to have it fixed by 6 p.m. Friday.

The weather also caused a change in Rapid City garbage collection schedule. Routes normally picked up on Thursday and Friday will be collected today (Saturday).

Postal carriers also were working late Friday to catch up on mail deliveries, according to Sonny Magnuson, customer service supervisor, who said the post office was dealing with snow-clogged streets like everyone else. He said mail delivery would follow normal delivery schedule today.

Reporters Scott Aust, Milo Dailey, Jomay Steen and Tim Velder contributed to this report.