A huge fire at Nairobi's main airport that damaged a key terminal and forced authorities to ground all flights was contained on Wednesday, Kenyan officials said. Parts of the roof of terminal 1 at Jomo Kenyatta International Airport collapsed in the fire, making it more difficult for fire crews to battle the blaze, which began in the early morning, dpa reported. All flights heading to the airport have been rerouted to Mombasa and Eldoret airports. Authorities have advised travelers to contact their carriers because of the disruptions expected. Nairobi's airport is the key hub for tourists visiting the east African nation and is also used as a transit point to reach other parts of Africa. At the peak of the blaze large flames and huge columns of thick black smoke billowed from the international arrivals and departure areas. No casualties have been reported and passengers who were on planes that landed but had not yet disembarked when the fire broke out have been evacuated to safety. "I urge members of public to be calm as the government investigates the cause of fire. Investigations have already started," David Kimaiyo, a police spokesman, said. The ministry said the fire was "massive." Its cause was not immediately known.