PITTSBURGH -- Freezing rain coated roads with slick ice that caused traffic problems across Pittsburgh Sunday, closing major roads and leading to at least one fatal accident.

Police began shutting down all major highways in Allegheny County, including the Fort Pitt and Squirrel Hill tunnels, after icy conditions began at about 7 a.m. Bus service was suspended for several hours but later resumed, although officials warned of delays, and the roads were later reopened.

"Anything we would have put down before it froze would have washed off, so you kind of had to address the icy conditions after they happened, because we didn't know where they were going to be," said Jim Struzzi of PennDOT. "So, it was a very difficult situation."

Some churches canceled services and meetings and other events were also called off.

Police said Amanda Dias, 22, of Derry, died after her vehicle went out of control on icy Route 22 in Murrysville and was struck by another car shortly before 7:30 a.m.

Dias was on her way to work at A-Vets in Monroeville when the crash happened. Her co-workers set up a burning candle as a make-shift memorial in her honor.

"We had been concerned that she hadn't reported for duty and we called her house and then her fiancé called us back to let us know about the accident," said Dr. Melissa Edwards.

The driver of the other car was not hurt. No charges have been filed.

Emergency crews across the commonwealth struggled to keep pace with the many traffic accidents, most of which involved damage and non-life-threatening injuries. Authorities asked drivers to remain home if possible and to use caution if they had to go out.

"If it's raining and it's winter, you have to know ice could be involved," said Pittsburgh Public Works Director Rob Kaczorowski.

In the Summer Hill section of Pittsburgh, one driver slid, got out of her car and was almost hit by another driver as Channel 11's cameras were rolling.

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VIDEO: Raw Video: Sunday Morning Ice

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Channel 11 was also at the scene of a six-car pile up on Negley Run Road in East Liberty. Aaron Nist of Zelienople was one of six drivers involved.

"Me and another vehicle were coming down the hill and hit a little black ice. We started doing 360s and we bumped into each other," said Nist.

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VIDEO: Freezing Rain Shuts Down Pittsburgh Highways

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Pennsylvania Department of Transportation Secretary Allen Biehler was injured Sunday morning in a fall outside his Pittsburgh-area home that department spokesman Rich Kirkpatrick said he believes was "ice-related."

Biehler, 65, who had been briefed throughout the morning on roadway conditions, was admitted to UPMC Mercy Hospital with several cracked ribs, a chipped elbow and a collapsed lung, Kirkpatrick said.

A hospital official said she had no information about his condition. Scott Christie, deputy secretary for highway administration, will take over in his absence.

Major roadways were shut down or allowed small amounts of traffic so PennDOT crews could salt Sunday morning. Roads closed included the Pennsylvania Turnpike. It was shut down in both directions between Cranberry and Irwin. The Parkway East, Parkway West, Interstate 79 and Veterans Bridge were also shut down.

According to Kaczorowski, 100,000 to 140,000 tons of salt were used to keep the roads as safe as possible.

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VIDEO: PennDOT, City Explain Road Treatments

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"They were real bad. You could skate on them. They were real bad," said driver Dennis Doud.

Doud was stuck in traffic for hours on Interstate 79.

According to a spokesperson at Pittsburgh International Airport, two of four runways remained open Sunday morning and planes took off and landed. However, the ice prevented travelers from getting to the airport.