Jaradat confessed, Israeli security sources said.
He suffered from back pains and a previous rubber bullet injury in his leg, as well as an injury from a tear gas canister that had hit his stomach, the security sources said.
While in custody, Jaradat was checked more than once by a doctor, and no medical problems were found. But after lunch Saturday, while resting, he was not feeling well, and emergency crews were called to the site. They could not save his life, security sources said.
Israel began an investigation and notified his family.
Rabo said Palestinians blame Israel for the death of "the martyr" and hold Israel responsible for the lives of all the prisoners on hunger strike.
Jaradat, the father of three, worked at a gas station, Rabo said.
"This incident should open the door to all sorts of investigation and accountabilities," said Hanan Ashrawi, a member of the Palestine Liberation Organization's executive committee. She called for Israeli prisons to be opened to the international community.
Human Rights Watch, meanwhile, called on Israel on Saturday to "immediately charge or release Palestinians detained without charge or trial for prolonged periods."
Palestinian prisoners in Israeli detention are one of many flashpoints in the Middle East conflict. Prisoners have launched hunger strikes in the past in hopes of bringing attention to their cause and pushing Israel to ease conditions or allow some prisoners to leave.
Israeli officials have pointed out that prisoners include members of extremist groups who have "blood on their hands."
In October 2011, Israel freed more than 1,000 Palestinian prisoners -- including hundreds serving life sentences for attacks on Israelis -- in exchange for one person: Israeli soldier Gilad Shalit, who had been held by Hamas for more than five years.