From midday on Saturday, the search focused on a region around the town of Lolodorf, 100km southwest of Yaounde, Cameroon's capital, where witnesses said they heard a loud explosion overnight, Cameroonian state radio reported.
Gabi Menezes, Al Jazeera's correspondent, said fog and dense forest were hampering the search operation on Sunday morning and that the Cameroon army might move its focus away from Lolodorf after searches had proved fruitless.
Radar-equipped helicopters, including one sent by the French military from a base in neighbouring Gabon, were looking at an area between three or four towns, a French diplomat in Cameroon said.
Mwai Kibaki, the Kenyan president, said he had sent a government team led by Chirau Ali Mwakwere, the Kenyan transport minister, to help the Cameroonian authorities find out what happened to the aeroplane.
"I wish to assure all that we have put in motion a mechanism to help establish the status of the Kenya Airways plane," Kibaki said in a statement.
Titus Naikuni, Kenya Airways Group's managing director, said on Saturday the authorities in Cameroon had picked up an automatically generated distress signal from the area where the plane went missing.
"As far as I know, the aircraft is updated in terms of maintenance and the pilots are also updated in terms of training," Naikuni said, adding that the plane was only six months old.
He said Kenya Airways had not decided whether to ground the three other 737-800s in its fleet.
The flight set off from the Ivory Coast's Douala airport, amid torrential rain, bound for Nairobi, Kenya's capital, and due to land at 6.15am (03:15 GMT) on Saturday.
Kenya Airways said the Douala control tower had received a last message from the aircraft right after takeoff.
The plane was said to be carrying 105 passengers and nine crew members.
The majority of the plane's passengers were from African countries, including 34 Cameroonians. Other passengers included, 15 Indians, five Britons and an American.
On Sunday, Haru Mutasa, Al Jazeera's Africa correspondent, quoted Kenyan authorities as saying that they cannot do much on their own and need the help of foreign nations. Also, they are reluctant to say anything until the aircraft is found.