The official says the investigation opened Tuesday.
Some 160 university students fell sick after a tuna meal on Monday, sparking protests by colleagues angry over the quality of basic services in the university hostel, the official said. The students blocked the main road leading to the university, and security forces fired tear gas to quell the protest.
The official spoke on condition of anonymity because he was not authorized to speak to the press.
The university's president was fired earlier this month after the first case of poisoning.