KUALA LUMPUR - Criminal investigators looking into the possibility of foul play by those on missing Malaysia Airlines flight MH370 may have found some leads to narrow down their probe in that direction, a Malaysian newspaper said.

They had, over the last few weeks, sifted through hundreds of closed-circuit television footage, not only from cameras in most corners of the Kuala Lumpur International Airport (KLIA) from which the Boeing 777-22ER twinjet took off, but mined those taken at a toll plaza 8.8km away, where most passengers would have passed to reach the airport.

Also mined were videos taken from the stretch of road leading to KLIA, the New Sunday Times (NST) reported.

Sources told NST that all those who boarded the plane had their movements recorded by CCTVs right up to the time they showed up at gate C1, in the West Zone of the airport's Satellite Building, where the plane was supposed to take off at 12.35am on March 8. It eventually took off at 12.41am.

The team carrying out this probe is separate from the International Investigating Team (IIT), which comprises agencies with expertise in satellite communications and aircraft performance.

Also roped in the IIT are the United Kingdom's Inmarsat, Air Accidents Investigation Branch (AAIB), and Rolls-Royce, China's Civil Aviation Administration and Aircraft Accident Investigation Department (AAID) as well as the United States' National Transportation Safety Board (NTSB), Federal Aviation Administration (FAA), Federal Bureau of Investigation and Boeing.

The IIT has among others been working to analyse data, including those obtained from radar and satellites, in narrowing the search area, which has since been centred in the Indian Ocean.

Police on Wednesday said they had "obtained some clues" on what might have happened to the flight, based on the statements recorded from more than 170 people. This number is climbing.

It was the same day that they cleared all 227 passengers of the flight. They, however, did not give the same clearance to the aircraft's crew.

Their probe had focused on four possible areas: hijack, sabotage personal problems and psychological problems.

Inspector-General of Police Tan Sri Khalid Abu Bakar had said police were looking at the crew of the flight, as the main "subjects of investigations".

Those they had interviewed included the passengers' family members as well as the crew's, including those of pilot Captain Zaharie Ahmad Shah, 53, and co-pilot Fariq Abul Rahman, 27.

While some details of the IIT's investigations had been released to appease family and media demand for information, the police said they would not divulge anything from their ongoing probe for fear that it could jeopardise their investigations.

"What is of paramount importance here is about getting to the bottom of this all.

"The police wouldn't, at any cost, risk this by making public at this point any findings that they had come to," sources said.

They are investigating the case under Section 130 (C) of the Penal Code, which deals with hijacking, terrorism and sabotage offences as well as the Security Offences (Special Measures) Act and Aviation Offences Act.

Among visuals extracted from the CCTV recordings were that of a senior crew member who had a cigarette before the six-hour flight to Beijing.

This visual was taken from the only available smoking area of the airport, located in its Satellite Building's East Zone.

After checking in, some two hours before the flight, many of those on board the plane had at some point made contact through their phones. Some of the passengers took the opportunity to shop for souvenirs.

Among those traced through the recordings were the two Iranians who went on board using assumed identities.

The duo, identified later as Pouria Nourmohammadi Mehrad, 19, and Seyed Mohammed Reza Delavar, 29, were described by Interpol as migrants being smuggled into Europe.

Investigators combing the recordings, first spotted them at the toll plaza in separate vehicles.

"One was in a taxi while the other was sent by a friend in a Proton Satria ... the vehicles stopped near each other and they walked in the same direction separately.

"They were trying hard to appear as if they didn't know each other at the airport.

"It was only much later that they pretended to bump into each other and shook hands, but after that they again kept a distance from each other, they were very calm throughout.

"Their hands were glued to their phones, texting non-stop ... it appeared as though they were taking instructions from someone. However, based on intelligence gathered, there was nothing suspicious that could link them to the plane going missing," the sources said.

Last month, information technology student Mohammad Mallaeibasir, 18, said the two had stayed in his apartment, here, the night before they left.

Mehrdad was his friend from high school in Teheran.

The recordings also traced the 19 Chinese artists and calligraphers, the second largest group that were travelling together on MH370.

After a visit to the the city centre in the scorching heat that Friday, they arrived at the airport much earlier before they checked-in.

As the group of artists reached the boarding gate, the head of their delegation, Hou Bo, received a call from their Malaysian host asking how they were doing. Bo told Daniel Liau: "Everybody is OK".

It is also learnt that Mr Fariq and chief stewardess Goh Sock Lay, 45, both communicated via messenger application WhatsApp about 11.30pm. This was the last exchange they made through the application.