Icy rain caused hundreds of traffic accidents Sunday, including crashes that killed at least seven people in the Northeast,

In New York City, officials called for additional assistance to deal with a flood of 911 calls caused by the dangerous conditions.

In New Jersey alone, state police reported more than 425 accidents, and officials throughout the region urged drivers and pedestrians to stay at home. One person was killed in an accident in Lebanon and another died in a crash in southern New Jersey, state police said.

The slippery conditions were especially bad in the areas north and west of New York City, but even in the metro area pedestrians reported slick and scary streets. City authorities received so many 911 calls related to the weather that nearby municipalities sent more than 30 ambulances to the city to assist emergency responders. Another 40 ambulances were kept on the job after hours, according to the FDNY.

Dispatchers had handled more than 3,700 medical calls by mid-afternoon, the FDNY said.

Because of the high call volume, people calling 911 with lower priority issues such as non-critical injuries were put on hold or received calls back from 911 dispatchers, the FDNY said. No serious injuries or deaths resulted from delayed responses, department officials said.

Public bus service was suspended in the Bronx. Weather officials initially expanded freezing rain advisories to include Manhattan, the Bronx, northern Queens and Staten Island - but by early afternoon the New York City advisories and many others in the region were lifted.

In Pennsylvania, icy conditions led to a deadly pileup involving more than 50 vehicles on Interstate 76. One motorist was killed and 30 others were hurt.Two others died in a crash involving multiple vehicles on nearby Interstate 476, police said.

In northeastern Pennsylvania, a man was killed after his car overturned on an icy road and he was thrown from it and hit by a commercial vehicle.

In Connecticut, police cited slippery conditions in a crash that killed an 88-year-old woman who struck a utility pole in New Haven.

By early afternoon, flood warnings were issued throughout New York City and in Rockland, Westchester, Fairfield, Hudson, Essex, Bergen, Union and Passaic counties. Such warnings indicate that "flooding is imminent or has been reported," according to the National Weather Service.

Some bridges and highways around the region were closed for ice, but by early afternoon some of those restrictions were being lifted. Delays were reported at airports around the region.

For updates on closures and accidents, check out New York and New Jersey transit sites.

Steve Schapiro, a spokesman for the New Jersey Department of Transportation, warned Sunday morning that conditions were extremely dangerous.

"There’s black ice so we’re advising drivers to stay home if they can until temps warm up," he said. "If you must be out driving, drive slowly and use extreme caution."

Later in the day, temperatures were expected to rise into the 40s, melting any ice, according to Storm Team 4. Flooding remained a danger, with 2 inches or more of rain expected to soak the region.

For updates on closures and accidents, check out New York and New Jersey transit sites.

The difficult conditions were part of a weather roller coaster of a weekend. On Saturday, an arctic front blasted the region with bitter cold and temperatures dropped into the teens and below, even as the sun shone brightly.

The coming week, however, is anticipated to be seasonable, with temperatures in the middle and upper 30s. Snow showers are expected on Wednesday.