Fairfax County officials charged yesterday that riot police were kept waiting for 90 minutes outside the gates of a Virginia prison camp that was the scene of a melee among inmates Sunday night.

County Police Chief John E. Granfield told the Board of Supervisors in a memorandum that 26 county officers and 25 Virginia state police troopers were at Camp 30 in western Fairfax by midnight but could do nothing until the facility's assistant superintendent arrived at 1:30 a.m.

Until then, there were only five guards and a sergeant on duty at the facility on West Ox Road, which was holding 152 inmates. "There was no one there to make a decision," said Fairfax Supervisor Elaine McConnell (R-Springfield). " . . . . This is sort of ridiculous to delay decision making."

Prison officials sought to play down the incident and criticism. "It sounds too much like politics to me," said Camp Superintendent David Smith, calling the incident "really fairly minor."

The two inmates slightly injured in the disturbance apparently had drunk a heady, homemade mash of fermented grapefruit juice, he said.

"They were drinking from some materials they had gotten out of the kitchen," said Smith. "By 11 they were pretty drunk, and later two of them got irritated with each other and started to fight."

Smith said that when others inmates tried to break up the scuffle, around 11:30 p.m., the fighting became more widespread, and continued for about 15 minutes.

Smith said nine inmates tested after the incident were intoxicated. He said the inmates apparently sneaked grapefruit juice, sugar and yeast out of the kitchen, and had allowed the materials to ferment in a plastic bag for three days. He declined to identify any of the inmates.