The United Nations (search) has ended an internal inquiry into the discovery of a secret listening device at the world body's European headquarters without finding out who planted the bug or when, officials said Friday.

The listening device was found during renovation work in an art deco room known as the Salon Francais (search) — which adjoins a main conference hall — where it could have been used to eavesdrop on any prive planted the device."

Although the device was only found this fall, the inquiry has already finished and will not be reopened, said a U.N. official, speaking on condition of anonymity.

Heuze added that she was unable to comment further on the bugging.

Well-placed security sources, however, questioned whether any major secrets could have been overheard because top government officials have security that includes electromagnetic waves to thwart eavesdropping systems.

"There's not much they could get here," said a second official, who spoke on condition of anonymity. "Most of the discussions are in public and they are recorded."

A Swiss surveillance expert who saw photographs of the device and said the parts were eastern European in origin.

"We can be sure that most parts of the components are from Russia," Patrick Daniel Eugster, head of Geneva-based Surveillance Consulting Group (search), told The Associated Press. "One part is from Bulgaria or Hungary."

Eugster said the bug had probably been manufactured three years ago, because more modern listening devices are smaller, adding that transmissions from the device would be so short that they would be very difficult to pick up.

The device could have been in operation in the run-up to the U.S.-led invasion of Iraq, judging from the age of the equipment.

The Salon Francais — or French Lounge — also is the venue for a weekly teleconference meeting between U.N. Secretary-General Kofi Annan and the head of the Geneva office, Sergei Ordzhonikidze.

The U.N. offices in Geneva were built in the 1930s as headquarters of the League of Nations. The Salon Francais is so called because it was decorated in art deco style by French artist Jules Leleu in 1935.

"Never truly renovated since this date, the room was starting to suffer from the assault of time," the French mission to the U.N. Geneva office said in a newsletter dated Monday.

Renovations were carried out by two teams, one contracted by the United Nations and the other by the French government. It was the U.N.-contracted team that discovered the bug behind a wooden panel, officials said.

China's ambassador to the U.N. in Geneva said Friday that his country's officials met with other delegations in any room which was assigned by the Ordzhonikidze's office.

"My personal feeling is that it's really disgusting and something must be done to stop these kind of activities," Ambassador Sha Zukang said of the bugging. "I hate it."

It was up to Beijing to decide if its officials will attend meetings in Geneva in the future, Sha added.