One hundred illegally parked cars were towed off D.C. streets to impoundment lots yesterday as the city government launched the latest phase of its crackdown on parking violators. The average number of towaways had been between 15 to 20 a day.

But 200 other card, designated with orange stickers that marked them for towing, eluded the wrecker because their owners returned before the blue-and-white tow trucks arrived, said Lloyd Sydnor, director of the towing division of the city's transportation department.

"I thought someone had stolen my car." said Sue-Pan L. Lee of Alexandria, who illegally parked in front of 1105 H St. NW during the morning rush hour. When she returned an hour later the car had been towed away.

The car was retrieved from an impoundment lot near Third Street and Massachusetts Avenue NW yesterday afternoon.

Metropolitan police reported that they were flooded with calls from motorists who, like Lee, thought their cars had been stolen.

Police gave callers the telephone numbers of the Department of Transportation, which operates the parking enforcement program.

Although dozens of cars had been hauled off the streets by 4:30 yesterday afternoon, Peter Bergin, head of the central violations bureau, reported that only seven people had come to pay the required $50 towing charge plus a parking fine, a requirement before a car could be removed from one of the city's two impoundment lots. Payment of the fine always had been required, but the $50 penalty became effective yesterday.

The towing operation is the next-to-last stage in a concentrated parking enforcement program started in October when 49 blue-suited civilians took to the streets and began issuing parking tickets at a rate of about 3,500 a day.

"We're clearing the streets," said Clyde Fairfax, assistant director for the towing program.

Yesterday, in addition to their usual ticket writing duties, these parking patrollers also affixed orange stickers with the words "tow" in black letters to car back windows that were parked in loading zones, at bus stops, or in front of fire hydrants.

"I did about 25 in Southwest," said parking control aide Gwendolyn Lee, because "they were on sidewalks."

Pedestrians have to walk in the street to get around them and some of the cars break up the sidewalks which my tax dollars have to pay to repair," she asserted.

"I have no feeling about it," said Edward Jones, another parking patroller when asked about the 12 cars he had designated for towing in the Cardozo area. "If they (7otorists) would read the signs they wouldn't have their cars towed."

The 25 tow truck drivers who picked up the marked cars yesterday left no indication that a car had been hauled in. A motorist who found his car missing had to call 724-8561, 724-8562 or 724-8573 -- numbers usually learned in a call to police -- to find out whether his car had been towed and to which of the two impoundment lots it had been taken. The two truck drivers are operating under private contract with the city.

Then the motorist had to go to 451 Indiana Ave. NW., pay the $50 towing fee, the amount assessed for the violation and any unpaid tickets charged to him before going to the lot to retrieve the car.

No money is collected at the impoundment lots, transportation officials said.

Cars are towed away between 7 a.m. and 7 p.m. on weekdays only. The central violations bureau has expanded its operating hours to open at 7 a.m. and remain open until midnight on weekdays so motorists can pay their penalties and get their cars.

The bureau also is open from 7 a.m. to 3:30 p.m. on Saturdays. The impoundment lots are open 24 hours a day except on Sundays.

The final stage of the program, to begin Jan. 29, is an expanded "booting" program to immobilize cars of motorists with four or more parking tickets. The program involves attaching a "boot," a metal device, to a wheel of a vehicle, preventing the car from being moved. After the motorist pays all outstanding tickets, the "boot" will be removed.