Environmental hazards in Gaza, such as raw sewage leaks, have been getting worse since Operation Cast Lead as even basic repairs are stalled by the ongoing blockade of the territory, a top UN official said Tuesday. The UN Environment Program will dispatch experts to Gaza for a 10-day mission, starting May 11, to assess how the three-week war has harmed the environment, said the agency's head, Achim Steiner. They will examine the destruction of water and sewage lines, disposal of hospital waste and possible asbestos contamination of the rubble of thousands of destroyed and damaged buildings. The experts, who have worked in areas of conflict in the Balkans, Afghanistan, Sudan and elsewhere in the Middle East, are to recommend an action plan, Steiner said in a telephone interview after touring Gaza. However, international aid officials have said it's unlikely that any significant repairs or reconstruction will move forward unless Gaza's borders reopen. Israel and Egypt have kept Gaza virtually sealed since a violent takeover by the Islamic militant Hamas two years ago, and have not eased restrictions since the end of Israel's three-week offensive in mid-January. Israel has allowed food and humanitarian supplies to be trucked in, but has said it will not reopen the passages fully unless Hamas releases an Israel soldier it captured almost three years ago. Israel launched the military offensive on Dec. 27 to halt years of rocket fire from Gaza on Israeli border towns. Egypt links a lifting of the blockade to an increasingly elusive agreement to form a unity government between Hamas and West Bank moderates. The blockade prevents the import of raw materials and spare parts for repairs and rebuilding. "The continued restriction of even the most basic goods, from simple cement bags to pipes, is essentially putting paralysis on any efforts to deal with repairs, never mind long-term rehabilitation," Steiner said. He noted that raw sewage keeps spilling into surrounding areas and into the Mediterranean because waste treatment stations cannot be fixed. "It is the continued non-action that is exacerbating a problem that did not end with the hostilities, such as sewage," he said. He noted that mountains of rubble, from homes destroyed in the war, have remained in place. "It's a frozen image of a conflict that ended over three months ago. Yet as you drive through, it is as if it happened last week," he said. "This speaks to the enormous frustration of the international community and the people in Gaza. What could have been done, simply cannot happen under the current circumstances." Israeli Foreign Ministry spokesman Yigal Palmor said that Hamas has used imports, such as pipes and cement, for building bunkers and rockets. "If there are restrictions, they are the fruits of years of shelling and rocket shooting, and those in power in Gaza should be held accountable for the situation in this area," he said.