Three medical workers today described their experiences in a refugee hospital during the massacre of Palestinian civilians in West Beirut but said they were unaware of the extent of the carnage around them until it was over.

The two doctors and an American nurse, who were in the Gaza hospital in Sabra refugee camp when the massacre took place Sept. 16-18, testified before the judicial board of inquiry that is investigating Israel's role in the events.

They said the hospital was overrun Sept. 16 by hysterical Palestinians telling of gunmen breaking into homes and killing the inhabitants. The medical workers described a night of almost nonstop surgery on the wounded and an eerie second night of the massacre when almost no wounded were brought to the hospital and little gunfire could be heard outside.

One of the key questions that the commission appears to be focusing on is why the Israeli Army allowed the Phalangist units to remain inside the refugee camps until the morning of Sept. 18, after receiving a number of warning signals about a possible massacre.

One of the witnesses, nurse Ellen Siegel of Washington, used her testimony to challenge an earlier explanation of the delay by Israeli Defense Minister Ariel Sharon.

Sharon testified last week that the Christian Phalangist militia units that were sent into the camps lacked sophisticated communications equipment and therefore needed extra time to bring their men out of the heavily urbanized area.

Siegel said the militiamen she saw in the camps had "many walkie-talkies" and that Israeli soldiers posted on the roof of a nearby building just outside the camps must have seen what was happening in the streets.

"I feel it is impossible that Israelis could not see from the top of that building what was going on and hear what was going on," Siegel said. "There was a system of communication, and Israel was in control there."

Siegel added: "It was horrible what was done in the holocaust. I will never forget that, but I will also never forget what happened in Sabra and Shatila. Justice must be done to all."

Israel Supreme Court Justice Aharon Barak, a member of the commission, replied, "Justice will be done."

Siegel and the other witnesses, Drs. Swee Chai Ang and Paul Morris, who are British citizens, said they saw a few bodies along a street in Sabra as they were escorted out of the camp by militiamen on the morning of Sept. 18.

Asked by Barak why they did not immediately report the massacre when they were turned over to Israeli Army officers, they said they had been busy inside the hospital and had not ventured out to find out the extent of the killing.

In testimony yesterday, Maj. Gen. Amir Drori, the Israeli Army's northern commander, said that by the morning of Sept. 17 he was suspicious enough of what was going on in the camps to order a halt to the Phalangist operation.

At a meeting later that day with Phalangist commanders, however, Drori and Israeli Army chief of staff Lt. Gen. Rafael Eitan agreed to allow the militia units to remain in Sabra and Shatila until the next morning.

Because of the communications problem, Sharon testified, he considered the more than 12 additional hours given to the Phalangist units in the camps a "completely reasonable" amount of time to withdraw.

In the commission's three public sessions so far, its members have indicated considerable skepticism about this decision by senior Israeli officers. Both Sharon and Drori were questioned closely on the point by Barak and commission chairman Yitzhak Kahan, the chief justice of the Israeli Supreme Court.

Eyewitness accounts from Beirut at the time of the massacre indicated that much of the killing was done during the night of Sept. 17-18. Today, however, the medical workers testified that they saw and heard little evidence of shooting that night.

They said that hundreds of refugees began streaming into the hospital during daylight hours of Sept. 16. When asked what was happening, Arab members of the hospital staff replied, "Ketaeb Phalangist , Haddad, Israel," according to Siegel.

Haddad is Maj. Saad Haddad, a former Lebanese Army officer who commands an Israeli-supported Christian militia in southern Lebanon. Many Palestinians in the camps said that Haddad's men were involved in the massacre, but this has been denied by Haddad and Israeli officials.

Morris testified that when he was turned over to Israeli Army officers on Sept. 18 he heard three of them refer to the presence of Haddad's men in the area.

Ang, an orthopedic surgeon, said she operated on the wounded through the night of Sept. 16, but she and the others said the number of casualties coming into the hospital on Sept. 17 slowed to a trickle. She said the last person she treated that afternoon was a wounded 11-year-old boy who told her he had hidden for hours among the dead bodies of his relatives until he was sure the militiamen had left his home.

On Sept. 18, the witnesses said, they were taken by militiamen out of Sabra along with about 20 other foreign medical workers who were in the hospital. Walking along a main street of the camp, Ang said, she saw three bodies and determined that they had been killed only a few hours earlier.

The medical workers said they were then interrogated by Phalangist soldiers and berated by a woman Phalangist officer for "not being Christian" because they had helped the Palestinians. After the interrogation, they said, they were taken a short distance and turned over to the Israeli Army.