A hospital spokesman said the 75-year-old Arafat was moved the day before because his condition had become more complex.
Senior Palestinian officials in Paris told CNN that Arafat was in critical condition in intensive care after drifting in and out of consciousness throughout the night.
Sources close to the Palestinian leadership told CNN's Christiane Amanpour that Arafat was not clinically dead, as some media have reported, but he is not registering things, is not recognizing people and is not speaking.
The sources also said the Palestinian leader's mental faculties had deteriorated in the past week.
The confusion over Arafat's health extended to Washington. Told about reports that the Palestinian leader had died U.S. President George W. Bush told reporters: "My first reaction is, God bless his soul.
"My second reaction is that we will continue to work for a free Palestinian state that is at peace with Israel."
Meanwhile, the Israeli military has been placed on high alert and Palestinian security forces are reviewing their plans to keep Palestinian territories calm in the event of Arafat's death.
On Thursday afternoon, French President Jacques Chirac was allowed to briefly visit Arafat's room. He also spent about a half hour with Suha Arafat, the Palestinian leader's wife.
Arafat's senior adviser, Nabil Abu Rudeineh, dismissed reports that the 75-year-old leader was in a coma, calling them "rumors."
"He is in the intensive care unit, as I said, because he is in need of several very advanced tests in the coming hours and days," Abu Rudeineh said.
In Ramallah, Palestinian Prime Minister Ahmed Qorei told reporters Thursday that Arafat was in stable but serious condition and still required urgent medical attention.
"He's under treatment in very honest hands, our friends the French," he said.
Palestinian Cabinet Minister Yasser Abed Rabbo said the Cabinet was "concerned now with the health of Chairman Arafat and we hope that he will overcome his illness."
A source close to Arafat told CNN the Palestinian leader was "OK and he's resting" and denied reports that he had lost consciousness. Another senior Palestinian source said Arafat had been medicated before tests Thursday morning and had simply slept through the night.
Let's just hope that the "other department" was the morgue, and the "treatment" was embalming