As independent medical investigations continued into the illness that has struck hundreds of Arab schoolgirls in the occupied West Bank, a senior Israeli official charged today that the outbreak was the work of "political factions" and said some arrests had been made in connection with it.

Shlomo Ilya, the head of the Israeli civil administration in the West Bank, said in a radio interview that the arrests began yesterday and that an investigation into the incident by Israeli authorities was continuing.

"We are collecting and observing more and more details and evidence that prove that a local political faction stands behind this show," Ilya said. "I am referring to those people who were in the hospitals, walking around, speaking with the doctors, trying to pressure them not to release those patients who the doctors said should be released."

Palestinians have charged that the illness, which first struck in the Jenin area two weeks ago and reappeared in two widely separated West Bank villages on Sunday, was the result of deliberate poisoning of the girls by Israeli authorities and Jewish settlers.

Ilya said "a very few" of the schoolgirls may have been genuinely ill, but that the vast majority of the more than 800 reported victims of the illness were not. The Israelis have attributed the epidemic to "mass hysteria" and "political provocation" by Palestinian nationalists.

Ilya said he hoped to be able to make public soon "details that prove it was the work of some political faction."

Israeli radio also quoted Dr. Shehadah Shehadah, general director of West Bank hospitals, as saying that about 20 percent of the schoolgirls were "suffering from known ailments that had nothing to do with poison" and that the others became ill because of "panic and fear."

The central committee of the Palestinian Red Crescent Society issued its own statement today saying there was confirmation that the "poisonous cases" were genuine. The statement condemned what it called "attempts by certain people to cover up the poison cases."

Meanwhile, two doctors from the World Health Organization arrived in Israel today to begin their own investigation. They joined two American doctors from the Centers for Disease Control in Atlanta, who arrived here Sunday at the invitation of the Israeli government.

The U.S. physicians, Drs. Philip Landrigan and Bess Miller, spent yesterday in Tulkarm and Jenin. They have made no statements regarding their initial findings, according to a spokesman for the U.S. Consulate in East Jerusalem.

Israeli officials, however, were quick to point out what they said were the conclusions of Dr. Frank Alter of the International Red Cross who investigated last week's outbreak in the Jenin area.

Dr. Baruch Modan, director general of the Israeli Health Ministry, said in a telephone interview that Alter's "impression was that there is no evidence of poisoning." He said Alter described the epidemic as a "mass phenomenon without an organic basis" and said that the West Bank population should be reassured that there is "no danger."

The first isolated cases of the illness were reported March 21 in the village of Arrabah near Jenin. This was followed by a larger outbreak in Jenin last week and reports of similar cases on Sunday in the villages of Yatta and Anabta.

Israeli officials maintain that the initial outbreak of the illness in Arrabah may have had a medical basis but that most of the others have not. Modan said the Arrabah cases "might have been caused by an environmental irritant, but not by poison."