The Iron Dome anti-rocket system intercepted two projectiles over the southern city of Netivot.The night before, the IDF also attacked 12 targets in Gaza in two waves of air strikes in response to Gazan rocket attacks that destroyed a Sderot factory on Saturday.The air force hit three targets in Gaza in the first weekend strike, and nine more targets in its second strike, including weapons-production centers and underground rocket launchers in central and southern Gaza.Some targets were marked ahead of time as “heavier targets” and were earmarked for attack, a senior security source said Sunday.“We are weighing events in Gaza. We are looking at activating additional steps,” the source said.Rocket attacks are coming from smaller Gazan terror groups, such as Popular Resistance Committees, but are not being launched by Hamas directly, the source said, adding that “Hamas has to be assertive against anyone who fires rockets. We see that happening here and there.We have to see it on a larger scale.”A rocket fired from the Gaza Strip hit the Sderot industrial zone on Saturday night, causing a plastics factory to catch fire. At least 10 firefighting teams worked to control the large flames amid the fear that the blaze might spread to other buildings.Magen David Adom said it had treated four people for light injuries.“The building went up in flames,” police spokesman Micky Rosenfeld said.“As a result of a direct strike, the whole factory was burned down,” he said, adding that “it took firefighters an hour and a half to put out the fire after police cordoned-off the surrounding area.”Rosenfeld said security assessments were made by the western Negev city’s mayor, municipality and police officials, who decided to keep area schools open Sunday.“All of the schools in the area are heavily fortified, and residents have been instructed to listen to Israeli police instructions and take cover in bomb shelters within 15 seconds of a warning siren going off,” he added.Ben Hartman contributed to this report.