Three couriers for the Arnold & Porter law firm have been charged with operating a major wholesale cocaine ring that, according to court testimony, conducted part of its business out of the firm's New Hampshire Avenue NW location.

The ring allegedly had been operating for five years and supplied a large number of other dealers, according to court testimony. Sources said the first information about the men's cocaine sales came from within the prominent law firm, which officials said had cooperated fully in the investigation.

The three men were arrested Jan. 4 after one of them, Tyrone A. Hines, 35, allegedly delivered five ounces of pure cocaine to an undercover D.C. police officer outside the 22nd Street NW entrance to the State Department. Four more ounces of cocaine were found in the men's car.

Police said the cocaine provided by Hines during four direct sales to the officer was 99.6 percent pure, about three to four times the normal strength sold on the street. Third District vice officer William J. Nealis testified during a preliminary hearing that the purity of the cocaine indicated the men had a direct connection with a cocaine importer.

Nealis said officers have been told that Hines and another of the men, Kevin Young Goode, went to New York to pick up drugs once or twice a week.

For two of the alleged undercover drug purchases, the officer met Hines in front of the firm's office. On one occasion, Hines placed a phone call and was soon joined by Goode. The two men then went to Goode's apartment across the street and returned with the drugs, according to court testimony.

Another time, Hines and Goode came out of the office building together and the officer allegedly bought an ounce of cocaine from Hines.

After their arrest, additional drugs were discovered during a search of Hines' house at 109 Urell Place NW and an estimated $100,000 worth of jewelry was found during a search of Goode's apartment at 1255 New Hampshire Ave. NW.

At the time of his arrest, Goode was on probation from Prince George's County until 1991 for a 1986 conviction for possession with intent to distribute cocaine.

He and Hines are being held without bond. The third man, Linwood R. Green Jr., 29, of 113 Q St. NW, was released on his personal recognizance. Green has worked as a courier at the law firm for six years, Hines for nine years and Goode, three.

A spokesman for the law firm said yesterday that he could not comment on the case. He said the three men are no longer employed there.