The Israeli commission that is investigating the massacre of Palestinian refugees in West Beirut resumed taking public testimony today with lawyers for some of the officials involved cross-examining witnesses.

The key figure in today's public sessions was Avi Dudai, the personal assistant to Defense Minister Ariel Sharon, who according to earlier testimony received an unconfirmed report of the massacre on Sept. 17, the second day of the slaughter, but failed to act on it.

Lt. Col. Reuven Gai, who at the time was acting as Sharon's military aide, was cross-examined sharply by Dudai's lawyer but reaffirmed his earlier testimony that he mentioned the report of 300 deaths in the Sabra and Shatila refugee camps to Dudai on the morning of Sept. 17.

The massacre, which according to Sharon resulted in the deaths of 700 to 800 Palestinian refugees at the hands of Lebanese Christian militiamen, ended the next morning.

Gai, who said he spoke with Dudai by telephone, acknowledged that he did not put the information about the 300 deaths into an official written Army report because it was unconfirmed.

The report of up to 300 deaths in the camps came from Lebanese Christian Phalangist commanders and was received by the Israeli Army headquarters in Beirut on Sept. 16, the first night of the massacre. It was relayed to Army headquarters in Tel Aviv, but nothing was done about it.

Dudai, one of nine senior Israeli officials who have been warned that they may be harmed by the outcome of the investigation, testified for a second time today in private.

Under cross-examination by the lawyer of another of the nine officials -- military intelligence chief Maj. Gen. Yehoshua Saguy -- Gai also said that his office received two reports from military intelligence on Sept. 15, the day before the massacre began.

The contents of the documents were not disclosed, but Saguy's lawyer apparently is trying to show that the Israeli government had been informed of the danger of widespread bloodshed in Lebanon after the assassination of Lebanese president-elect Bashir Gemayel.