Out of the tons of rubble of the American Embassy, rescue workers today pulled the body of the U.S. Marine who had stood guard in the front lobby and two soiled U.S. flags.

Even as U.S. marines continue their grim search for bodies, missing documents and evidence in the embassy ruins, more U.S. diplomats have been flown here to fill in for those who were hurt or killed and to aid in the rescue effort.

U.S. officials, still confused about the number of dead in the Monday explosion that shattered the central section of the embassy, expressed despair that the full extent of casualties may never be known. U.S. Embassy spokesman John Reid said, however, that the death toll has risen to 24 people confirmed dead and 25 others missing and presumed dead.

Ambassador Robert Dillon said today that the bodies of eight Americans and a British man serving with the U.S. marine have been recovered and another nine Americans are still missing and presumed to be dead.

U.S. officials said a government plane would arrive here Friday to pick up the bodies of the Americans and return them home Saturday.

The White House announced that a high-level delegation headed by Undersecretary of State Lawrence Eagleburger would go to Beirut to return with the bodies, United Press International reported. President Reagan is scheduled to meet the plane this weekend when it arrives at Andrews Air Force Base.

The body discovered today was that of Lance Col. Robert McMaugh, 21, of Manassas, Va. McMaugh, who is survived by his parents, a brother and two sisters, was on temporary assignment in Beirut as part of a team conducting training of Lebanese Army forces, the Defense Department said.

Dillon acknowledged that U.S. casualty estimates did not fully coincide with figures given out by Lebanese officials and said the two groups are seeking to reconcile the differences.

"I want to tell you that it may be some days before we realize the full extent of our loss," Dillon said. "Despite our best efforts, the work of clearing debris takes time, as it must be done in an orderly and safe manner."

An embassy employe, attempting to keep accurate records of those killed in the explosion, said, "Some people may never be identified, their bodies may never be recovered."

Rescue teams, including Department of Defense bomb experts, combing through the rubble found metal fragments that the U.S. experts thought might be shards of the bomb. But they still were uncertain about how the blast occurred, who had done it or why.

Lebanese Foreign Minister Elie Salem told reporters that four men have been arrested in connection with the bombing but he refused to give any details about them or their activities. He also indicated that the leads turned up so far in the investigation were paltry.

"We do not know, and we are not at liberty to reveal the little information that we know from preliminary investigations," Salem said.

Investigators' attention still remained focused on pro-Iranian Shiite Moslem factions, such as the Islamic Jihad Organization, which claimed immediate responsiblity for the blast.

The prevailing theory is that someone in a van laden with explosives charged the heavily guarded circular driveway of the embassy to detonate the bomb.

For the Lebanese, there appears to be a mixture of many fears in the aftermath of the explosion: the fear that the Israelis would dig in in southern Lebanon, the fear that Lebanon would continue its orgy of violence and the fear that the United States would forsake this war-torn country.

At a press conference today, Salem accused Israel of exploiting the bombing for propaganda advantage. He said his country was the victim of U.S.-Soviet rivalry and gave scholarly reminders to the United States about its responsibility as a great world power.

Salem seemed especially concerned about reports that Israeli Foreign Minister Yitzhak Shamir and Defense Minister Moshe Arens had claimed that the explosion justified the continued Israeli presence in Lebanon.

Coming in the aftermath of the collapse of talks between Palestine Liberation Organization Chairman Yasser Arafat and Jordan's King Hussein, the devastation of the American Embassy here raised fears that the Americans would abandon a search to mediate peace in the Middle East.

In a strong effort to convince the Americans of the importance of their role here, Salem said, "We are . . . aware that great nations know there is a price to pay for commitments."

The Lebanese foreign minister, reflecting the familiar feeling of many Lebanese through eight years of civil war, said that Lebanon's problems had come from outside and the bombing of the U.S. Embassy was a "freak operation."

"It is unfortunate that whoever is the target, Lebanon is the victim," Salem said. "Israel fights the PLO, the real victim is Lebanon. Syria fights Israel and the real victim is Lebanon. The Americans and the Soviets compete, the real victim is Lebanon."