Israel-Gaza updates: 17 more hostages released, including 4-year-old American girl, officials say

The first pause in hostilities between Israel and Hamas in nearly seven weeks came into effect on Friday morning.

The four-day cease-fire started slightly later than the planned 7 a.m. local time, as the Israeli military carried out last-minute airstrikes on the war-torn Gaza Strip.

The Israel Defense Forces released a statement announcing the completion of "its operational preparations according to the combat lines of pause." Amid the early morning hours in the area of Gaza's largest hospital, Al-Shifa, Israeli troops destroyed a "route of underground tunnels and a number of tunnel shafts" that the IDF alleged was used by Hamas, which rules the enclave.

"The war is not over yet," the IDF added. "The suspension of fires for humanitarian purposes is temporary. The northern Gaza Strip area is a dangerous war zone and it is forbidden to move around."

"For your safety, you must remain in the humanitarian zone in the south of the Strip," the IDF continued. "It is only possible to move from the north of the Strip to its south via Salah al-Din Road. The movement of residents from the south of the Strip to the north will not be allowed in any way."

The release of some hostages being held by Hamas and other Palestinian militant groups in Gaza, in exchange for the release of some Palestinian prisoners in Israel, is expected to begin at 4 p.m. local time.

-ABC News' Bruno Nota, Joe Simonetti and Morgan Winsor

ABC News has learned more details about how the tentative release of Israeli hostages will play out from an Israeli source with direct knowledge of the current plan.

The Red Cross will pick up the hostages and transfer them through Egypt to Israel, the source said.

Once on the Israeli side a specially trained group of soldiers will identify them and cross-reference them from a list, according to the source.

Then the hostages will be offered a chance to speak to loved ones by phone, and then the adult hostages will be debriefed by the Shin Bet, the source said.

Women and girls released will be offered a rape kit, according to the source.

The hostages will be reunited with their families and be transported to several hospitals, the source said.

-ABC News' Matt Gutman

Israel Defense Forces spokesperson Daniel Hagari provided an update Thursday evening as families await the negotiated return of some of the hostages from Hamas.

He said they received the list of women and children who will be part of the first group released and the IDF has informed their families.

"This is a hard and tense evening for us all," Hagari said.

He reiterated that the current negotiation with Hamas is "not the end of the process of returning the hostages, but the beginning of it."

"Our hearts are with the families, and we will continue to accompany them, to keep them updated with the reliable information that we have," he said.

-ABC News' Dana Savir

All areas of the Gaza Strip will receive medical supplies and fuel and cooking gas during the cease-fire, according to Hamas.

In a statement, Hamas said Israeli planes will stop flying over the southern Gaza Strip entirely during the cease-fire. Planes will stop flying over the northern Gaza Strip for six hours a day during the cease-fire.

Israel confirmed that it has received a list of hostages who will be released and officials are in contact with the hostages' families.