Atabakzadeh said the breakage in the pipeline between Aghajari and Deylam had happened last week and described the damage caused by the oil spill as "irreversible."A storm has hampered clean-up operations, a senior environmental official told Mehr news agency. "All equipment is ready to clean up the spill but the work is being slowed down by the storm," Omid Sadighi said.Iran is the second largest crude producer in the Organisation of Petroleum Exporting Countries (OPEC).