Police were yesterday investigating a possible drugs and gun running link in Friday's violation of Kenya's airspace by a light aircraft.

Officers were searching for a Toyota Corolla station wagon said to have been loaded with "suspicious cargo" from the plane, but which escaped a police dragnet thrown immediately it was established the plane had landed illegally.

Eyewitnesses said one of the bags, which was torn while being loaded onto the vehicle, emitted "a whitish substance which is being analysed to establish its nature".

Contacted for comment, the Machakos deputy police boss, Mr Kegode Kidiavai, said: "We have taken samples of the powder and will forward them for testing. However, investigations are still at a preliminary stage."

The plane, said to have been on private charter from Somalia, landed at 2 pm on Friday at an airstrip at Masinga Dam, at Yatta, near Machakos, senior police sources said.

The operation appeared to have been well-coordinated, with the plane being met by a convoy of four mini-buses and a saloon car, which ferried the passengers towards Nairobi.

Suspicious onlookers immediately alerted the police, who threw a series of roadblocks around the area and stopped one of the buses, seizing 17 passengers. They took them to Masinga police post, where they were being held last night.

Another four immigrants were arrested later, bringing to 21 the total believed to have been on the plane. Forty other Somalis and seven Kenyans were being held on suspicion of having helped them to gain entry to the country.

Among the Kenyans was a mini-bus driver, his conductor and two agents of the refugees who had no identity papers.

The entire Eastern Provincial Security team travelled to Masinga to investigate the violation, but Cabinet Minister Julius Sunkuli, who is in charge of the security docket, assured Kenyans that the country's airspace was safe.

"The security forces are on full alert to ensure that the incident is not repeated," said Mr Sunkuli in an interview with the Sunday Nation in Nairobi.

Mr Sunkuli denied claims that most of the 21 illegal immigrants who were arrested after the incident were women and children after their male colleagues escaped the police dragnet.

"That information is very misleading as far as our records are concerned because once the police received the tip off they quickly mounted road blocks and arrested most of the Somali immigrants," the minister said.

Asked whether the recent sacking of airline controllers and replacement with retired colleagues and new recruits could have been taken advantage of by the masterminds of the Friday charter flight, Mr Sunkuli denied it saying the incident was an isolated one which had little to do with the airline controllers.

The minister maintained that the Kenyan airspace was well protected and covered by the police, the Air Force and the Directorate of Civil Aviation and there was therefore no cause for alarm.

But even as he spoke, security experts warned that the full impact of the breach had not been appreciated.

Nearly 70 per cent of the country's hydro-electricity is generated in the Masinga area and experts said the breach had exposed major weaknesses that could be exploited to sabotage the country's power supply.

The airstrip where the plane landed is used by KenGen and Kenya Power and Lighting Company Limited staff.

The aircraft landed at Kamburu airstrip, just hundreds of metres from the strategic Gitaru power generation station. The Kamburu, Gitaru, Kiambere and Masinga dams are strategic national installations as they generate over 70 per cent of the country's power supply.

International flights into the country are only supposed to land at the Jomo Kenyatta International Airport, Moi International Airport Mombasa, Moi International Airport, Eldoret or the Wilson Airport in Nairobi. Lockichoggio airport is reserved for flights leaving the country for southern Sudan only.

A herdsman, who witnessed the episode from yards away, told the Sunday Nation: "The vehicles, a matatu and a small white car, arrived within 15 minutes of each other. Fifteen minutes afterwards, the aircraft arrived."

"After the plane landed and taxied to a halt, three men jumped off, others in the plane threw the children and baggage into their arms as the women trooped out. In about three minutes, the vehicles were speeding away and the plane on the runway on its way back to the sky," the startled eyewitness who sought anonymity said.

Detectives investigating the incident confirmed that they were investigating the drug-trafficking theory. Meanwhile, UNHCR country representative George Okoth-Obbo has denied the involvement of any of his staff in the syndicate.