Israel opened the Kerem Shalom Crossing into the Gaza Strip on Monday to facilitate the transfer of supplies to the Palestinians as defense officials warned that Hamas was possibly digging tunnels under the crossings, to be used to destroy them. On Monday the Defense Ministry permitted the transfer of 57 trucks carrying supplies - such as basic foods and medicine - into Gaza. Five ambulances were also allowed in. The Karni Crossing was supposed to open but was closed due to security threats. Bezalel Treiber, head of the Defense Ministry Crossing Directorate, told The Jerusalem Post that there was intelligence that Hamas was planning to target the crossings. He said that the Palestinians were desperate to receive the supplies and that due to the risk of "terror tunnels," Israel was running the crossings under a "new operational model." He would not elaborate on what that was. "We have many terror warnings that they want to hit the crossings," Treiber said. "For that reason, we operate under heavy security." Meanwhile Monday, the IDF Gaza Coordination and Liaison Administration (CLA) coordinated the transfer of a truck carrying 1,000 units of blood donated by Jordan. The ambulances were supplied by the Geneva-based International Committee of the Red Cross and came from the Red Crescent in Jerusalem. ICRC spokeswoman Dorothea Krimitsas said the latest shipment of medical supplies followed an earlier delivery Sunday but was unlikely to cover the needs of Gaza's hospitals. CLA commander Col. Moshe Levy said that the IDF was in daily contact with a number of international organizations to facilitate the transfer of humanitarian supplies to the civilian population in Gaza. "The CLA is in constant touch with international authorities that operate in Gaza as well as with various Palestinians in order to follow the humanitarian situation in the Gaza Strip and prevent a crisis," Levy said. "For that reason, we are allowing the daily transfer of supplies - including medical equipment, medicine and basic foods - into the Gaza Strip."