Prince George's County and U.S. Park Police yesterday investigated tire tracks on the frozen Potomac river leading to a car-sized hole in the ice, but suspended their search operations late yesterday because of darkness, both agencies reported.

The National Park Service's helicopter "Eagle" first spotted the tire tracks about one mile south of the Woodrow Wilson Bridge, at the end of River Bend Drive, in Prince George's, according to Park Police.

County police then investigated the area on foot for more than an hour, but were unable to determine if a car was under the ice. The ice is one foot thick in some places, according to police spokeswoman Irene Hill.

County police requested the help of the District of Columbia police's harbor division, but the division was unable to send its own boats because of the ice, Hill said.

The search operation, which started at about 4 p.m., was called off at sunset. It will resume this morning, according to Hill.

While police looked for the car, hundreds of people skated on the Potomac, ignoring the warnings of Metropolitan Police that the ice might be several inches thick only near the shore, and therefore dangerous.

"There's no law on the books preventing them from skating," said Official Daryl Wing, of the harbor division. "Since the cold spell started we've gotten hundreds of calls from people wanting to know if they can go ice-skating. We tell them there's no law against it, but we warn them," he said.

The only applicable law pertaining to use of the Potomac is a "contact" law, prohibiting someone from making contact with the water. "If they fall through the ice we might cite, I suppose, but by then it might be too late," he said.

The National Weather Service yesterday forecast temperatures in the 20s and 30s today - as well as a 70 per cent chance of snow tonignt. As much as 2 inches of snow is predicted for parts of the Washington area. When added to the 8 inches that already has fallen this month, Washingtonians might be experiencing the snowiest January since 1957, weather officials said.

The unusually cold weather is heading the area for its coldest winter since World War II. Normally the daily temperature average for January is 35.6 degrees, according to national Weather Service statistics. This year the average has been 24.9 degrees, which is identical to the averages in 1940, according to weather service figures.

Although the average daily January temperature - 35.6 degrees - is above freezing, so far this month there have been only four days (the 5th, 8th, 11th, 16th) when the average temperature went above 32 degrees, according to weather officials.

Cold weather continued play havoc with life on the East Coast. Florida officials said 150,000 migrant farm workers in Florida may have lost three lucrative months of employment, thanks to the killer freeze that has cost the state's vital agriculture industry $150 million.

Florida Gov. Reubin Askew on Saturday declared a state of emergency in an attempt to qualify for U.S. assistance. The declaration also made the migrant workers eligible for unemployment compensation to which they ordinarily are not entitled.

Maryland Gov. Marvin Mandel yesterday flew in a helicopter onto icebound Smith Island in the Chesapeake bay with a pledge to seek federal assistance for the island's embattled 600 residents. National Guard helicopters have been keeping the residents supplied with fuel and food, according to Wilroy Bradshaw, an island resident.