People were coming and going at the house at 13135 Haddock Rd. in Dale City at all hours of the day and night earlier this summer, their cars blocking the quiet residential street. Annoyed neighbors complained to Prince William County officials.

The final straw was a recreational camper parked in the driveway. In a letter to the county zoning office last month, State Del. David G. Brickley (D-Prince William) summed up neighborhood feeling and complained that people were living in the vehicle and that its electronic equipment was interfering with neighborhood radio and television reception.

It turned out that the premises were occupied by good guys instead of bad.

A zoning official dispatched to investigate the complaints was told by one of the occupants of the house that the U.S. Drug Enforcement Administration was using it as the base of operations for surveillance of a suspected heroin ring.

Sager Williams, the Prince William zoning administrator, said he called the county police, who confirmed that the DEA was using the house.

Williams then gave a copy of Brickley's letter of complaint along with a letter he wrote in reply--explaining that the house was exempt from zoning restrictions since it was being used by the federal agency--to the Potomac News of Manassas, which published them on Monday.

"I thought it was amusing," Williams said yesterday. "We get complaints like this all the time. 'The people next door keep awful hours' or 'They're living in their Winnebago.' This time the usual had an unusual twist at the end."

Just how unusual became apparent only yesterday.

When told by an inquiring reporter of the story in the Manassas newspaper, DEA special agent Bill Schnepper confirmed yesterday that the house had been used in a drug investigation.

But that was hardly supposed to be common knowledge, he said, because the investigation is still going on.

"I didn't know about the published report--that everyone knows now," Schnepper said, adding: "They really did that?"

Both zoning administrator Williams and county police said yesterday they thought the investigation had ended.

I wouldn't have said anything if I thought the investigation was still going on," said Williams.

Police Capt. J. Sullivan, who had confirmed the DEA involvement with the house for the Potomac News, said, "We'd look pretty silly telling about the house if the operation wasn't finished. I was told by County Police Sgt. Mike Johnson that it was over." Johnson could not be reached for comment.

Schnepper, reached at the DEA regional office in Washington, said he was upset to hear that the use of the house on Haddock Road by his agency is public knowledge. But he said, "it will not affect the operation . . . which is ongoing at this time."

He would not comment further on the investigation or say for what purpose--if any--the house is still being used.

No one was at home at 13135 Haddock Rd. yesterday, and the neighbors said they thought no one had been there for about three weeks.