Israel-Gaza updates: Israel says ground operation underway in southern Gaza

The cease-fire between Israel and Hamas has allowed some residents of Gaza to return home for the first time to survey what was left.

"I said I would go back to my house and tidy it up and sweep ... but I came and found it destroyed. I am very shocked by what I saw," Um Raed Al-Najjar told ABC News.

Another resident, Muhammad Al-Najjar, said his 80-year-old cousin lost his two-story house.

"His life's work was gone," he said.

"We are civilians and have nothing to do with anything," Muhammad Al-Najjar continued. "This whole street has nothing to do with anything 'political.'"

Muhammad Al-Najjar added, "We were all waiting for the truce because we were psychologically tired -- we became mentally ill. The majority of people will lose their minds. … What is the fault of a child who is 2, 4 or 3 years old? Did he participate in the war?"

The process of transferring a fifth group of Hamas-held hostages has begun, a source in the Israeli Prime Minister's Office with direct knowledge of the operation told ABC News on Tuesday evening.

It was unclear how long the process would take to be completed. It took about an hour on Monday night for hostages to be transferred from the Gaza Strip back to Israel.

-ABC News' Jordana Miller and Morgan Winsor

All 50 women and children hostages who were in the original swap agreement have been released, Israeli Prime Minister Benjamin Netanyahu said.

"We are obliged to complete this outline and bring about the release of all our abductees -- women and children and later, everyone -- without exception," he said.

The Israel Defense Forces "is prepared to continue fighting" in the Gaza Strip and is "using the days of the pause as part of the framework to learn, strengthen our readiness and approve future operational plans," according to IDF Chief of Staff Lt. Gen. Herzi Halevi.

"The return of the hostages is a bright light for us all," Halevi said in a statement on Tuesday. "It is also further evidence of the results of significant military pressure and resolute ground operations, which created the conditions for the return of our civilians home."

Halevi vowed "to apply the same strength" if needed in northern Israel, where he said some residents have been evacuated from their homes amid clashes along the border between Israeli forces and Lebanese militant group Hezbollah.

"The IDF's ground operations in Gaza City, a dense and complex area, aim to achieve a worthy and necessary goal," he said. "We know, if required, how to apply the same strength in the north, in order to return you safely to your communities, cities and this beautiful and important region of the country."

-ABC News' Morgan Winsor