Nine Northern Virginia residents were arrested during the weekend on charges of possessing or distributing cocaine after police raided an Arlington motel where they said crack, a highly concentrated form of cocaine, was being sold.

"The significance of this particular arrest . . . is it's our first encounter with crack," said Lt. John S. Karinshak of the Arlington County vice squad.

The officer said the operation that police raided Saturday night had established "a crack house" at the Embassy Motel, 1900 Jefferson Davis Hwy., near National Airport, the officer said. A crack house is a place where cocaine is processed into the concentrated form and then sold to individual customers.

The officer compared crack houses to "a floating crap game: it moves from place to place and nobody knows where it's going to be but the players."

Karinshak said that a small quanity of crack was found in the hotel and officers seized four guns and smoking apparatus there.

A police officer, working part time as a security guard at another motel, had noticed activity at the Embassy Motel and alerted Arlington police, he said.

Joseph Roderick of 3028 Manning St., Alexandria, was charged with conspiracy to distribute cocaine.

Eight others were charged with possession of cocaine. They are Ternia M. McKnight of 4937 Manitoba Dr., Johnnie M. Crews of 212 Lynhaven Dr., Katherine Quander of 2708 Dewitt St., April S. Scruggs of 3028 Manning St., Jerome Dyson of 117 S. Hudson St., Carlton Funn of 5121 Holmes Run Pkwy., all of Alexandria; Anessa R. Ford of 2905 Fairmont St., Falls Church, and Jimmy Wright of 3459 S. 22nd St., Arlington.

All were being held yesterday at the Arlington County Jail.