The signal was from a mobile phone believed to be that of one of the ten passengers who were aboard the aircraft.
Jomo Kenyatta International Airport control tower reported that it lost contact with the plane at 5:20pm.
The caravan aircraft registration number 5Y-CAC had 8 passengers and 2 crew members.
East African Safari Air Express, the plane's operator, said in a statement that the 12-seater aircraft departed from Kitale for Nairobi at 4:05pm.
A search and rescue team has been mobilised by the Kenya Civil Aviation Authority, Aircraft Accident Investigation Department, and KWS.
"At present, East African Safari Air Express has no knowledge of the location or condition of the aircraft or its occupants," the statement released on Tuesday said.
Relatives and next of kin have been asked to convene at Weston Hotel for more information.
They can alternatively seek more details via the crisis number 0706 305 305.
"We are in the process of contacting the next of kin and family of the passengers on board.We pray for the safety of the passengers and of our crew," East African Safari Air Express said.
UPDATE: Weather is a challenge for the on going search & rescue operations, a national police chopper is already up in the sky but weather condition is the problem.
Following the missing aircraft, National Disaster Management Unit (NDMU I) appeals to Members of the public to volunteer information which may lead to quick rescue and recovery.
The suspected area of search is along the route from Kitale to Abadares, Thika and JKIA Nairobi. If any information you are advised to call; 999, 911, 112 among others.
For cordination, you may contact 0722644085.
Multi-Agency Search Operation on both land and aerial (air) is going on. Agencies involved includes National Police Service, Kenya Wildlife, National Disaster Management Unit, Kenya Red Cross, Kenya Forest Service, Aviation Accidents Investigation among others.
-The Star