( CNN ) -- At least 12 people were killed and more than 130 injured Tuesday when two explosions hit an Interior Ministry building in the Nile Delta city of Mansoura , Egyptian media reported . Previously , the semi-official Al Ahram news agency reported 14 dead , citing the country 's Health Ministry . It was not immediately clear why the death toll was lowered . Among the people injured is the head of the security directorate of Dakahlia governorate , state-news agency MENA said , citing Health Ministry officials . Part of the building collapsed after the explosion , MENA said . One blast occurred on one of the top floors of the building and was followed by a car bomb , MENA reported . Egypt 's interim Prime Minister Hazem al Beblawi called it a terrorist incident and said the perpetrators will not go unpunished . Without directly blaming the Muslim Brotherhood , the party that backs ousted President Mohamed Morsy , he called that party a terrorist group in his statement to the nation . The Muslim Brotherhood tweeted Tuesday that it `` strongly condemn ( ed ) the cowardly bombing in # Mansoura & express deep condolences to families of the victims # Egypt . '' An Egyptian court in September ordered a ban on activities by the Muslim Brotherhood and froze its finances , in a move that diminished its political power . Witness : Heavy damage at the site . Ahmed El Shabrawy was at his home when he heard a loud blast . He told CNN it took him five minutes to run to the building where he saw a man pulled by other residents from the rubble of the building . He estimated that dozens of cars were damaged , and there was a large area around one of the blast sites were there was `` heavy material damage . '' At least 10 ambulances had responded to the scene , he said . So many people rushed to a blood donation center that workers had to turn people away , he added . CNN first learned of the blasts from Twitter . Upcoming vote on proposed constitution . The blasts come in the lead-up to Egypt 's referendum on a new constitution , which will be held January 14 and 15 . The draft constitution would ban religious parties and put more power in the hands of the military . A military coup in July unseated Morsy , who was democratically elected . Since then there have been almost daily protests , some of which have ended in violence and other bombings , such as one on December 12 when 20 police recruits were injured in a car bomb attack . On Sunday , Ansar Jerusalem , a self-proclaimed jihadist group responsible for several terrorist attacks , mainly in the Sinai Peninsula , issued an online statement calling on army and police members to quit . `` With your staying in these institutions from evening to morning , you are incurring the anger of Allah , '' the statement said . No group immediately claimed responsibility for Tuesday 's bombing . Morsy , an Islamist leader , has endured a series of legal troubles . He and 132 others will face trial for escaping from prison in 2011 , state media reported Saturday . Morsy will be tried along with members of the Muslim Brotherhood and Palestinian Hamas , al Ahram reported . He is also charged with raiding other prisons , and killing soldiers and officers in Rafah , it said . He has been in custody since his ouster . CNN 's Saad Abedine contributed to this report .
The acting PM calls Muslim Brotherhood a terrorist group but stops short of blaming it . Two blasts hit an Interior Ministry building in Mansoura . Blasts come as nation prepares for a referendum on a new constitution . More than 130 people were injured , media reports .