An Egyptian military official told Ma'an the army was preparing for a major operation in Sinai "to clean it up from terrorist and criminal cells."
The army official said "coordination is ongoing between the Egyptians and the Israelis to bring military vehicles, troops and jets into Sinai to fight terror."
The 1979 peace treaty between Israel and Egypt has imposed strict controls on deployments in the desert peninsula.
Egyptian soldiers seized seven boxes of ammunition at a tunnel opening in the al-Barahmeh neighborhood of Rafah on Sunday, the Egyptian official said, adding that the army had deployed to the area to stop infiltrators entering through tunnels.
Egyptian soldiers and armoured vehicles have deployed heavily along the Gaza border for two weeks.
Egypt's army used sand to seal several smuggling tunnels along the border near the Brazil neighbourhood on Sunday, a Ma'an reporter said.
The health ministry in Gaza warned Saturday that the tunnel closures had caused a fuel crisis that is affecting hospitals.
Ministry spokesman Ashraf al-Qidra said hospitals' fuel reserve was down to 20 percent. Hospitals are using smaller generators to minimize fuel consumption, all-Qidra told Ma'an.
The Hamas-run government has appealed for help from the Arab, Islamic and international communities as well as the World Health Organization and human rights organizations, he added.
Meanwhile, Egypt has not informed Palestinian officials when it will reopen the Rafah crossing, the government in Gaza said Sunday. Due to Israel's blockade, Rafah crossing is the only terminal for most Palestinians in Gaza to leave the enclave.
Egypt's army closed the border terminal on Friday. Egyptian officials said the closure was due to unrest in Sinai following the army's ouster of President Mohamed Mursi.
Several Islamist militants have publicly threatened to carry out raids in reprisal for Mursi's dismissal on Wednesday.
On Sunday, militants blew up a gas pipeline in El-Arish, a day after gunmen killed a Coptic priest in the North Sinai city.
That came after armed supporters of Mursi had stormed the provincial headquarters in El-Arish and raised the black banner of Al-Qaeda-inspired militants on Friday night, an AFP correspondent said.
Also Friday, militants launched coordinated rocket and machine gun attacks on Egyptian army and police checkpoints in the Sinai, killing one soldier and wounding two others, Egyptian medical sources said.
A police station and a military intelligence building in the border town of Rafah also came under fire from rockets, security sources said.
The Israeli army said Tuesday that it had "authorized" the deployment of Egyptian military reinforcements in Sinai.
"The Egyptian military activity in the Sinai is coordinated with Israeli security elements and authorized at the most senior levels in Israel, in order to contend with security threats in the Sinai that pose a threat to both Israel and Egypt," the army said in a statement.