A senior official in the Belgian Foreign Ministry said today that documents allegedly sold to East European diplomats by a Belgian civil servant were of so little importance that "we've been asking ourselves what they could have been used for."

The official, who spoke on the condition that he not be named, said the documents allegedly leaked by Eugene Michiels, a trade specialist in the ministry, described trade problems within the European Community and revealed what is common knowledge among journalists who have covered the institution and its member countries.

In a related development, Reuter reported that Belgian investigators had uncovered a Brussels electronics firm acting as a front for Soviet technology spies. However, senior government officials, including Foreign Minister Leo Tindemans, said they had no knowledge of this discovery.

Tindemans reportedly met this morning with the prosecutor in the case and with officials in the Foreign Affairs and Justice departments to clear up conflicting reports about the investigation.

According to the Reuter report, security agents working on the Michiels case discovered the electronics company's activities. The company, whose name was not divulged, was reportedly run by Soviets and employed some Belgians.

It was not clear whether the two espionage cases were linked.

During the weekend, the Belgian government ordered home one Soviet and three Romanian diplomats, along with an employe of the Romanian Embassy who did not have diplomatic status. The expulsion followed the arrest 10 days ago of Michiels, who directs the Foreign Ministry department responsible for coordinating Belgian trade with the 10-nation community and with its equivalent in the Soviet Bloc, which is known as Comecon.

Michiels, 60, has admitted selling documents to the East European diplomats and is being held on corruption charges at a Brussels prison, according to the official and other news reports here.

The Belgian government learned of Michiels' illegal activities from an East European agent who defected to the West. The official refused yesterday to give any details about the defector.

Most of what Michiels sold were documents outlining the positions of community countries on such matters as prices of agricultural products. These "position papers" are not usually made public--only the final decisions handed down by the Council of Ministers are. But most European community observers, he said, are aware of the divisions and alliances among the 10 countries.

"With what he sold, it is clear that Belgium and even the community have nothing to fear," the official said. He added that "it is very possible" that the alleged East European agents were using a classic spy technique on Michiels--asking for relatively harmless materials at first so he could be blackmailed later into delivering more vital information. But Michiels, he said, was due to retire at the end of this year and would have been useless to his customers after that.

Although Michiels' department helps organize meetings of community foreign ministers as well as the regular summits between leaders of those countries, the Belgian civil servant had no access to classified information, according to the official.

He said his assessment that the materials sold were insignificant is based on several investigations by the Foreign Ministry, which traced many of the files Michiels had solicited. Investigators also recovered from Michiels' home some documents that "gave us some idea of what the rest was like," the official said.