Officials of the Virginia Electric and Power Co. said yesterday new information has caused them to change their minds about the pencil and paper clip they earlier thought played a major role in the release of radioactive gas from the North Anna nuclear power plant.

In a statement, the company said that even though the pencil and clip were found blocking an automatic valve control switch after the incident, a detailed check of computerized records showed that the switch was in fact not blocked at the time the gas was released.

"It was operating as it was supposed to," a Vepco spokesman said. "It was just not a factor. We're still looking into the reason why this happened."

The gas was released about 7:30 a.m. on Sept. 25, about 90 minutes after the plant had shut down automatically because too much water was entering a water heater through a ruptured metal tube.

Officials of the company and the Nuclear Regulatory Commission both said the amount of radioactivity released into the air was so slight that it could not be detected by NRC monitors set just outside the fence surrounding the plant.

Several workers inside the plant received higher than usual doses of Xenon 133, the NRC said, but these were still "well within allowable limits."

Yesterday, Ken Clark, an NRC spokesman in Atlanta, said inspectors from his agency are reviewing Vepco's new report, but could not confirm it.

"We're still interviewing workers and looking over log books and all the other records," Clark said. "At this time we have no way of confirming what Vepco says."

On Monday, the NRC said its inspectors also had seen the pencil and paper clip and thought that by blocking the automatic water control switch they had "contributed" to the release of radioactivity.

Vepco officials said yesterday they did not know why the switch had been wedged into the nonautomatic position after the gas was released or exactly when the pencil and clip had been slipped into the control panel. They said the same thing may have happened "on occasions in the past."

With the pencil and paper clip ruled out. Vepco said it now has no explanation why the gas escaped.

"You can take [the accident] through a series of things and see what happened," said Thomas Tenzel, a public relations officer for Vepco. "But it's hard to see why it happened."

He said the plant has been shut for the next three months for normal refueling.