Defense Department officials expressed concern yesterday about the status of the six or seven military people apparently separated from the other Americans held hostage in Lebanon or aboard the Trans World Airlines plane hijacked June 14.

None of the military persons known to be on the airliner has been seen in televised appearances arranged by the hijackers, one official said, heightening fears that passengers who had military identification cards are being held separately by Shiites more radical than those handling the main group.

U.S. officials have told The Washington Post that some intelligence reports on the hostages' whereabouts state that at least six persons, mostly if not all military personnel, appear to have been moved to Baalbek in eastern Lebanon near the Syrian border.

Asked about this yesterday, White House spokesman Larry Speakes said: "It is our belief they are in Beirut."

Another White House official, who declined to speak for attribution, said "there are conflicting reports" about where the hostages are located. "The judgment that the State Department and the White House have made is that the prisoners are in the Beirut area. Maybe they are there today and somewhere else yesterday," the official said.

Baalbek is a quick drive of about 45 miles from Beirut, facilitating a shell game with a small group of captives if the Shiites opt to try in that way to foil U.S. intelligence surveillance and possible military rescue operations.

A worst-case theory offered by some U.S. specialists on Lebanon is that some radical Shiites may be insisting that U.S. military hostages be kept in Baalbek to discourage attacks by Navy bombers from the USS Nimitz offshore against the walled army compound in the ancient city frequented by Iran's Revolutionary Guards.

U.S. intelligence officials have indicated that the guards helped plan the bombing of the U.S. Marine compound at Beirut International Airport in October 1983, when 241 U.S. servicemen were killed.

This suspicion, and the fact that the army complex is so isolated that bombing there would not endanger civilians in the area, has put Baalbek high on the list of possible U.S. retaliatory targets, as the Shiites know from strikes made there by French and Israeli bombers.

Aboard the carrier Nimitz are A6E medium bombers that could demolish such sturdy military complexes as the Sheik Abdullah army barracks in Lebanon.