The IDF left Gaza Tuesday morning after a rare raid into the southern Strip in which at least 40 Palestinians were detained. The army released all but a few of the arrested who were transferred to Israel for further questioning. Overnight Sunday, large infantry forces from the Givati Brigade, backed by tanks and helicopters, swept into Gaza through the Sufa Crossing and took up positions at nearby homes located a kilometer-and-a-half from the border. Using loudspeakers, the soldiers called all men aged 16 to 40 to gather at the mosque, where they were loaded onto a truck and driven to a nearby IDF base. No fighting was reported during the short foray and IDF sources said the detained Palestinians would be questioned by the Shin Bet (Israel Security Agency) and if found to be innocent, they would be released. Southern Command sources said that the purpose of the operation was to search for terror tunnels being dug in the area and to flatten areas used frequently by terrorists to launch rockets at Israel. On Monday, one Kassam rocket and seven mortars were fired from the Gaza Strip without causing injuries. IDF sources said they had obtained intelligence about several tunnels that were being dug near the security fence and that Hamas planned to use them to infiltrate into Israel and kidnap a soldier like they did last June when Cpl. Gilad Schalit was captured. Recent days have seen a drop in Palestinian rocket fire, but four soldiers were wounded in a mortar attack on the Erez Crossing on Sunday. Hamas claimed responsibility for the strike as well as the Monday's mortar fire. Transportation Minister Shaul Mofaz called for an escalation in IDF operations against Hamas. "We need to reach a point that they have paid a heavy price for the Kassam rocket fire," he told The Jerusalem Post, adding that until now the IDF operations had not achieved that goal. Also Monday, Egyptian security forces seized 1.5 tons of explosives in central Sinai possibly on its way to be smuggled into Gaza via tunnels under the Philadelphi Corridor. In December, Egyptian police discovered half-a-ton of explosives in Sinai on its way to Gaza. Security officials said that the announcement was a "positive sign" indicating a possible shift in Egyptian policy and a decision to begin cracking down on weapons smugglers and operators along the border with Gaza. Defense officials have complained in recent months that the Egyptian Border Police force deployed along the border with Gaza was not effective in stopping the flow of arms and explosives to Palestinian terror groups in Gaza.