A passenger plane with about 150 people on board has crashed into buildings in a densely populated district of Nigeria's main city of Lagos. Nigeria's Civil Aviation Authority said there were no survivors on board the Dana Air plane. The cause of the crash is not yet known. Thousands of onlookers gathered at the crash site as rescue services searched the rubble for survivors. President Goodluck Jonathan has declared three days of mourning. The plane crashed in Iju neighbourhood, just north of the airport. It is not yet clear how many people may have died on the ground. TV pictures showed chaotic scenes as crowds swarming the crash site, some helping pass along hoses to douse the smoking embers of the plane. Smoke billows The commercial aircraft was flying from the Nigerian capital, Abuja, to Lagos when it crashed and burst into flames. There were chaotic scenes as onlookers and emergency services rushed to the crash site. At the crash site, reporters saw plane wreckage including a detached wing scattered around and the body of the plane lodged into a building. The wreckage was on fire and black smoke billowed. Several charred corpses could be seen in the rubble. "We heard a huge explosion, and at first we thought it was a gas canister," Timothy Akinyela, 50, a local newspaper reporter who was watching a football match with friends in a bar near the crash site told Reuters. "Then there were some more explosions afterwards and everyone ran out. It was terrifying. There was confusion and shouting," he said. The plane did not to appear to have nose-dived into the building but to have landed on its belly, careering into a furniture shop and a print works, reports said. Casualties on the ground may have been minimised because it was Sunday and the commercial buildings were likely to have been empty. An investigation is under way, but in difficult night-time conditions, says the BBC's East Africa correspondent Will Ross. Officials told AFP the cockpit recorder had been found and given to police. Technical problem In a statement, President Jonathan declared three days of mourning and said he had ordered the "fullest possible" investigation into the crash. The crash had "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", the statement reportedly said. The weather at the time of the crash was overcast - but there were none of the storms that regularly strike the city. On 11 May a similar Dana Air plane - possibly the same one - developed a technical problem and was forced to make an emergency landing in Lagos, our correspondent adds. Nigeria, like many African countries, has a poor air safety record, though some efforts have been made to improve it since a spate of airline disasters in 2005. Dana Air's website says it operates Boeing MD-83 planes to cities around Nigeria out of Murtala Muhammed Airport. The airport is a major hub for West Africa and saw 2.3 million passengers pass through it in 2009, according to the most recent statistics reportedly provided by the Federal Airports Authority of Nigeria.