Pakistani security officials cordoned off the U.S. Consulate in the volatile southern city of Karachi on Wednesday after a bomb threat, but found no explosive, officials said. Unidentified callers phoned a police help line and the consulate, saying a bomb had been planted inside the consulate and would detonate at 2.30 p.m. (0930 GMT), said Fayyaz Leghari, chief of operations for Karachi police. Police blocked access roads to the consulate and searched the surrounding area and found no bomb. They were continuing their search, but suspected it was a hoax, he said. "We have taken all precautionary measures. We cannot take any risk," Leghari told The Associated Press. A spokesman at the U.S. Embassy in the capital Islamabad confirmed the consulate received a bomb threat and that it was working with authorities to determine its authenticity.