U.S. investigators began their inquiry here into the Jonathan Jay Pollard espionage case today amid extraordinary security and a virtual news blackout imposed by the Israeli government.

Some members of the U.S. State Department and Justice Department investigating team interviewed principals in the case in Tel Aviv, Israeli officials said, but U.S. and Israeli officials refused to identify who was questioned or how far the investigation had progressed.

Three key members of the U.S. team, whose flight from New York was delayed in London, did not arrive until this evening, and investigators were not expected to begin dealing with the most substantive aspects of the case until Friday.

Israeli officials refused to answer any questions about the U.S. inquiry team's movements, declaring that a "blackout" had been ordered at the highest levels of the government.

One senior Israeli official, who for years had been a cooperative source, could offer no information.

"The blackout is so black that I can't say anything," said the official, who is close to Prime Minister Shimon Peres. "It's so black that except for the people directly involved, nobody is being told anything."

U.S. officials, both from the investigating team and the U.S. Embassy in Tel Aviv, also refused to discuss any aspect of the questioning sessions.

Security around the head of the U.S. team, Abraham Sofaer, the State Department's legal adviser, was tightened after a CBS television camera crew was forced off the Jerusalem-Tel Aviv highway this morning while Sofaer was driving in an embassy car to his first appointments.

A U.S. Embassy spokesman refused to comment on the incident, but official sources said that the CBS camera crew's car overtook an embassy security car following Sofaer's embassy limousine on the four-lane highway and that security officials became "nervous" when they saw a passenger lift a "large black object," which later turned out to be a video camera.

After sending instructions to Sofaer's limousine to pull ahead, the sources said, the embassy security men forced the CBS car into a guardrail, causing some damage.

The decision to maintain a low profile for the U.S. inquiry, an Israeli official source suggested, may reflect concern in the Israeli intelligence establishment about how much Israel should be perceived to be contributing to a conviction of one of its own alleged agents. Jonathan Jay Pollard, a 31-year-old civilian intelligence analyst for the U.S. Navy, was arrested outside the Israeli Embassy in Washington on Nov. 21 and has been charged with selling top-secret intelligence documents.