Negligence on the part of security officials was the reason for Prime Minister Manmohan Singh's [Images] motorcade deviating from its planned route, Kerala [Images] Home Minister Kodiyeri Balakrishnan said on Wednesday.

Balakrishnan met Dr Singh and apprised him of the reasonsfor the security flaw that took place while the prime minister was on his way from the airport to Rajbhavan on Tuesday night.

Preliminary investigation has found that negligent handling of the prime minister's motorcade was the reason for the security lapse, Balakrishnan told reporters.

He said stringent action would be taken against erring officials.

The state government has suspended Balachandran, Circle Inspector, City Armed Reserved Camp and in charge of
the pilot vehicle on Tuesday night.

Police said the driver of the pilot vehicle Shiju, who was taken into custody after straying off the prescribed route
for the Prime Minister's convoy, was let off on Wednesday after questioning.

Shiju, a private taxi dirver hired for the job, was released after he gave in writing to police that he did not deviate from the route and only followed the instructions of the police officials in the car, police said.

Shiju was admitted to a private hospital by his relatives after he complained of chest pain, family sources said.

Kerala Chief Minister V S Achuthandnan has sought details from the director-general of police as the lapse came as an embarrassment to the state police responsible for the security of the prime minister's movements in the city.

The convoy turned back after a police constable on duty on the prime minister's route stopped the pilot car on seeing it going the wrong way.

As a result of the security mess-up, the prime minister reached the Raj Bhavan about 15 minutes behind schedule, the sources said.

Defence Minister A K Antony, Union Overseas Affairs Minister Vylar Ravi and Achhuthananandan were part of the prime minister's convoy.

The state government has asked Additional Director General of Police Jacob Punnose to inquire into the lapse and submit a report within 48 hours.

The incident came as a major embarassment to the Kerala police as at least three rounds of traffic drills had been conducted ahead of the prime minister's visit.

The government had instructed the police to make meticulous security arrangements in the wake of the e-mail to President A P J Abdul Kalam and the prime minister last week.

Balakrishnan, who cut short his visit to Delhi to return to Thiruvananthapuram from Chennai, told reporters on his arrival at the airport that the government viewed the incident seriously and a detailed inquiry will be conducted to avoid recurrence of such incidents in future.

Asked why tourist vehicles were used in the motorcade, he said it had been the practice for years.

However, in view of Tuesday night's incident, the government will review the present mechanism and take steps to introduce new arrangements, if necessary, he said.

The minister said the incident could not be seen as an intelligence failure.