Ethiopia had received no threat from terrorist groups prior to the crash Monday of an Ethiopian Airlines flight carrying 90 people, a government spokesman said. 'We had not received any threat before from terrorist groups whatsoever,' Shimeles Kemal, state minister for communication, told selfnews. The Boeing 737 reportedly caught fire five minutes after takeoff from Beirut airport, he said. Witnesses reported seeing flames as the plane plunged into the sea. 'The cause of the accident is being investigated and the government will disclose the information as soon as the investigation is over,' he said. Lebanese President Michel Sleiman also said earlier that foul play was not suspected. Ethiopian Airlines dispatched a team of experts to Lebanon to probe the incident. Ethiopia is grappling with rebellions in remote southern and eastern regions led by groups it describes as 'terrorist' and has been routinely threatened by the Al Qaeda-linked Shebab group in neighbouring Somalia, a country it invaded three years ago to remove the Islamists from power. Communications Minister Bereket Simon said a national day of mourning had been declared to honour the victims. 'A day of mourning has been declared today by the government following the crash of the Ethiopian Airlines flight in Lebanon... The day is today and for one day,' he said. A Lebanese defence ministry official said the Boeing 737 exploded into four pieces before crashing shortly after takeoff at 2:30 am (0030 GMT). Investigators were trying to determine whether lightning had hit the jet. 