A blast was heard Friday morning in the Karni crossing area on the Gaza Strip border. Three United Nations workers were hurt and sustained light to moderate wounds.

Gaza sources initially reported that the three were hurt by a shell fired by an Israeli tank force. The IDF denied striking in Gaza and said the blast was caused by the firing of a Palestinian mortar shell. IDF elements described the incident as a "failed Hamas launch."

However, a subsequent IDF inquiry suggested the explosion may have occurred after a tractor had climbed over an explosive device.

The last attack from Gaza took place on Passover eve. Several hours before the Seder, a Qassam rocket fired from northern Gaza exploded in an open area near a Sha'ar HaNegev Regional Council kibbutz.

The Color Red alert sounded in the area, as well is in Sderot. No injuries or damage were reported.

Elior Levy contributed to this report