SEPANG, March 16 — The police investigation into Malaysia Airlines flight MH370 now encompasses all of the flag carrier’s workers who came into contact with the plane, police said today.

Speaking during the official press conference here today, Inspector-General of Police Tan Sri Khalid Abu Bakar said investigators were continuing to pursue four possibilities — hijack, sabotage, psychological, and personal problems — in the case now classified under Section 130C of the Penal Code.

Khalid said investigators have also “intensified” their checks into the airline’s workers including ground staff.

“All, even those responsible for towing the plane,” the IGP said when asked about the extent of MAS employees who will be probed.

Earlier today, authorities said police interviewed engineers who may have come in contact with the plane.

The police investigation into the jetliner that went missing on March 8 was now classified under Section 130C of the Penal Code, which covers hijacking, sabotage, and terrorism offences, among others.

Khalid added that action under the Security Offences (Special Measures) Act (SOSMA) — which had replaced the Internal Security Act (ISA) — could be taken in the investigation.

Khalid also said that some foreign intelligence agencies have cleared all 227 passengers aboard the Boeing 777-200ER in their background checks, but did not name the agencies.

Prime Minister Datuk Seri Najib Razak said yesterday that MH370 was diverted deliberately after someone on board switched off the plane’s communications systems, an act which experts say would require extensive flight experience.

He also announced that the search in the South China Sea would be called off and pointed to two corridors where the plane could possibly be located based on satellite data: a northern arc from northern Thailand to the border of Kazakhstan and Turkmenistan in central Asia, or a southern one from Indonesia to the southern Indian Ocean.

*An earlier version of this article incorrectly referred to Section 130C of the Penal Code as Section 130 (c).