By DALE GAVLAK The U.N. refugee agency chief Antonio Guterres speaks during a press conference in Amman, Jordan, Wednesday, March 13, 2013. Guterres, warns of an “explosion” in the Middle East, if the Syrian conflict continues, and calls on governments to approve “extraordinary funds” to meet an enveloping humanitarian crisis. (AP Photo/Raad Adayleh) AMMAN, Jordan (AP) — The U.N. refugee chief says his agency is working with Jordan to bolster security at a camp for Syrian refugees where reports of drug trafficking, prostitution and other crimes have emerged. Antonio Guterres says the Zaatari camp near the Jordanian-Syrian border now is de facto Jordan’s fourth-largest city, with a “complex” environment. He told reporters in Amman on Wednesday that security will be “very strongly increased” and special measures will be undertaken to stop criminal activities. Guterres spoke after meeting Prime Minister Abdullah Ensour to discuss mechanisms to ensure that the rule of law is carried out in the camp. He provided no details. The two also discussed contingency planning for an expected spike in refugee numbers. Jordan currently hosts 450,000 Syrian refugees.