A doctor at the largest hospital in Gaza has reportedly said Israeli forces have found nothing in their search for a Hamas command center at the facility.
Israeli troops are said to have seized several buildings within the Al-Shifa compound since launching a raid on Wednesday.
On Friday, they said that they have found the body of a soldier held hostage by Hamas nearby.
Israeli Prime Minister Benjamin Netanyahu told US-based CBS Television on Thursday that there are "strong indications" that hostages were held in the hospital.
On Friday, Israel Defense Forces officials said Hamas fighters have also been present at other hospitals in Gaza.
Footage they released shows a motorcycle purportedly found in a basement of one hospital. A military officer says Hamas used the vehicle to transport hostages.
Hamas denies using hospitals for military purposes.
Reuters news agency interviewed a doctor at Al-Shifa Hospital by phone on Friday. He is quoted as saying that Israeli tanks and troops have been moving all over the compound.
The doctor said, "They have found nothing. They have found no single resistance. No single gunshot against them within the hospital area."
Israel is showing no sign of backing down, and a chief military spokesperson suggested on Friday that the offensive may be expanded.
He said they are determined to advance their operation "wherever Hamas exists, including in the south of the strip."
Gaza is facing a humanitarian crisis, and international criticism of Israel's actions is growing.
On Friday, the country's war cabinet said it will allow two fuel tankers into the enclave each day to support the sewage system, adding that the measure comes in response to a request from Washington.