Two persons were burned, one critically, in a fire yesterday morning at an electrical substation at the Naval Research and Development Center in Carderock, officials said.

The two men, both electricians, were performing routine maintenance when the fire broke out about 9:25 a.m. in electrical switching gear, according to Navy security spokesman Richard McNamara.

Electrician Bill Hoffit, who was burned over more than 80 percent of his body, remained in critical condition last night at the Washington Hospital Center, according to an official there.

The other man, whose name was not released, was treated for less serious burns at Suburban Hospital and released, a hospital official said.

MacNamara said it was unknown what caused the fire, which left sections of the center -- located along the Potomac near the Cabin John bridge -- without power throughout the afternoon yesterday.

"We had an industrial accident. Some switch gears exploded," MacNamara said.

MacNamara said reporters were not being allowed into the facility to see the damage, and a guard at the entrance told the Associated Press he was under strict orders to "turn the press away."

Operations at the research center ordinarily slow down during the weekend, MacNamara said, limiting the disruption caused by the power outage. "It was very fortunate that this happened over the weekend," he said.

Firefighters at the center were the first to arrive on the scene, and the fire was out soon after it started, MacNamara said.

Nonetheless, three firefighting units from Montgomery County were dispatched to the scene, according to a county fire department spokesman.

Potomac Electric Power Co. employes were also sent to assist in the incident, a Pepco spokesman said.