CAIRO — At least 161 students have been hit by food poisoning at Cairo's prestigious Al-Azhar University, in the second such incident this month, prompting President Mohamed Morsi to call Tuesday for an investigation. The health ministry said the students had been hospitalized after eating tuna salad served Monday at the university's canteen. Morsi called for an investigation by the ministries of health and education, the presidency said. The food-poisoning case sparked protests by studnets angry over the quality of basic services in the university hostel. The students blocked the main road leading to the university, and security forces fired tear gas to quell the protest. Earlier in April, 561 Al-Azhar students were hospitalized after eating contaminated food at the university's dormitory. That incident triggered student protests that lead to the university president being sacked. Al-Azhar, has thousands of students in fields such as law, medicine and business and is also the Sunni Muslim World's most prestigious theological center. — Agencies