President Goodluck Jonathan on Sunday declared three days of national mourning for those who lost their lives in a Dana plane crash in Lagos, according to a statement from Aso Rock Presidential Villa.The Dana Air flight from Abuja to Lagos crashed a few kilometres to the airport with 147 people on board, according to an airline official.The statement said Jonathan had cancelled all his public engagements scheduled for tomorrow and had also directed that the Nigerian flag be flown at half-mast for the three days of national mourning.The President has also ordered the “fullest possible investigation’’ into the crash.The statement said that In compliance with the President’s directive, the Minister of Aviation, Princess Stella Oduah, had already left Abuja for Lagos to oversee the crash investigations and present an interim report to the Federal Government as quickly as possible.“The President joins all Nigerians in mourning all those who lost their lives in the plane crash which has sadly plunged the nation into further sorrow on a day when Nigerians were already in grief over the loss of many other innocent lives in the church bombing in Bauchi State.“President Jonathan assures air travellers in the country that every possible effort will be made to ensure that the right lessons are learnt from the tragic loss of valuable lives in today’s plane crash and that further measures will be put in place to boost aviation safety in the country.“He prays that God Almighty will grant the families of the victims of the plane crash the courage and fortitude to bear their irreparable loss,’’ said the statement signed by Dr Reuben Abati, Special Adviser to the President on Media & Publicity.Meanwhile, a spokeman for the airline, Mr Tony Usidamen, said that 147 people were on board the plane, 139 of them passengers.In another development, investigations into crash have begun, the Director-General of the Nigeria Civil Aviation Authority (NCAA), Dr Harold Demuren, told the News Agency of Nigeria (NAN) on phone on Sunday in Lagos.Asked if they were survivors among the passengers on board when the plane crashed, he said: “We don’t believe there are survivors.“I am talking to you from the scene of the crash. Right now our thoughts and prayers are with the families.”Rescue efforts are being hampered by a huge crowd of onlookers, miscreants and sympathisers.NAN correspondents at the crash site at Iju, on the outskirts of Lagos, report that the inaccessibility of the site has made it difficult for rescue teams, which include the police, Red Cross, Army, FRSC, Nigeria Air Force and Fire Service to get to the plane.The General Manager, Lagos State Emergency Management Agency, Dr Femi Osanyintolu, told NAN that the building on which the plane fell must be demolished for any rescue operation to take place.He also said that they had to be cautious in demolishing the building because of its location in a residential area.In a related development, a contract staff with the British American Tobacco Company, Mr Isaac Daniel, who resides in a two-storey building where the plane crashed, said he had lost everything to the incident.Daniel said that he resided at the ground floor of the building with five members of his family.He said that all his family members survived the crash but lost their certificates to the fire that engulfed the plane, adding that he was not at home when the incident occurred.Eyewitnesses said that three lifeless bodies had been removed from the building.