The condition of those hospitalised is "reasonable," said spokeswoman Sivan Weizman, but did not elaborate.
Advocates for the prisoners said their health is deteriorating.
The advocacy group Addameer visited five hunger strikers in Israel's Ramle Prison last week and said they were weak and barely able to move.
Issa Karakeh, the Palestinian minister for prisoner affairs, told a news conference today that some of the hunger-strikers are in serious danger.
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The Israeli human rights group B'Tselem said that as of April, 191 Palestinians were in administrative detention. Overall, Israel is holding more than 5,000 Palestinians convicted or accused of anti-Israeli activity.
Since 2012, Palestinian prisoners have staged a series of hunger strikes, sometimes as individuals and sometimes in larger groups.
The current hunger strike was launched April 24 by 80 detainees and more have joined since then.
Weizman said that 240 Palestinian prisoners are currently on a hunger strike, while Karakeh put the number at about 300, and said about half of them are administrative detainees.