(Reuters) - At least two rockets were fired into southern Israel on Saturday but both exploded in desert areas causing no damage or casualties, a military spokeswoman said.

"Last night an explosion was heard in the Arava area in southern Israel ... Following an examination in the area it was determined that the rocket was probably a Grad, and the incident is currently being reviewed," the spokeswoman said after the remains of a first rocket were found.

Palestinian militants in the Gaza Strip, ruled by Islamist Hamas, have fired Grad rockets at Israel from the coastal territory in the past, and Israel says militants have also crossed into the Sinai region of Egypt to launch similar attacks.

The remains of a the first rocket landed in a remote area about 50 kilometers (31 miles) north of the Red Sea resort city of Eilat, close to the border with the Sinai Peninsula.

The second rocket landed about 100 kilometers further north, deep in the Negev desert near the town of Mitzpe Ramon, the army said.

An Egyptian security source said a sweep of the Sinai border area was carried out and he was certain the rocket was not launched from Egyptian territory.

"The rocket wasn´t launched by Palestinian elements or saboteurs in Sinai, as the area is fully secured on the Egyptian side. We have swept the border area ... but no evidence was found that the rocket was launched from Egyptian land."

Sinai governor Abdel Wahab Mabrouk also ruled out a launch from Sinai, saying: "This is illogical under the tightened security measures."

The desert border between Israel and Egypt was relatively quiet for three decades after the two countries signed a peace treaty in 1979. But Israel says that since the fall of Hosni Mubarak, Cairo has lost its grip on the Sinai.

In April, Israel said a rocket fired from the Sinai hit Eilat, without causing casualties, and last August cross-border infiltrators shot dead eight Israelis. Israeli soldiers repelling the attack accidentally killed five Egyptian guards.

Israeli Prime Minister Benjamin Netanyahu said after the April rocket that the Sinai had turned into a "kind of Wild West" exploited by Islamist militants, with Iranian help, to smuggle in weapons and stage attacks on Israel.

(Additional reporting by Yousri Mohamed in Ismailia; Editing by Andrew Roche) (© Thomson Reuters 2012. 06/16/12)