The search for a missing Malaysia Airlines flight carrying 227 passengers and 12 crew members entered a third day on Monday as a multi-country search effort took hold.
About 40 ships and 22 aircraft from nine countries are taking part in the search effort, which was expected to resume at first light.
Fuad Sharuji, vice president of operations control at Malaysia Airlines, told CNBC on Monday that the airline had received several pieces of information that may be related to the missing aircraft but have so far proved negative.
"At the moment, we are as desperate as anyone else to find evidence at all," he said.
There are two oil slicks that are being analyzed by aviation authorities to confirm if they came from the flight. Officials are also looking at the possibility the jet disintegrated in mid-flight, Reuters reported citing a senior source.
"Certainly something unexpected happened and it had to be catastrophic in nature in order to prevent the crew from communicating it," said John Goglia, former member of the National Transportation Safety Board in the U.S. "That doesn't rule out mechanical failure and it doesn't rule out some sort of activity by person or persons unknown."
Some officials on Sunday had tied their hopes to debris. A Vietnamese navy plane spotted an object in the Gulf of Thailand that they suspect belongs to the Malaysian jetliner, the Civil Aviation Authority of Vietnam said on its website Sunday.
(Read more: Possible part of missing jet found, Vietnam says)
During the airline's press conference earlier this weekend, Malaysia's Department of Civil Aviation director-general Azharuddin Abdul Rahman said that there was still "no sign" of the aircraft and search efforts had intensified.
"The outcome so far [is] there is no sign of the aircraft… The research started at 7 a.m. this morning until 7 p.m. this evening. However, the ships will continue to do the search overnight," he said.
Rahman of Malaysia's Department of Civil Aviation added the search radius had been increased to 50 nautical miles from 20 nautical miles, and would include the Straits of Malacca following reports earlier in the day that the airline may have "turned back" from its scheduled route before disappearing over the South China Sea.
(Read more: Missing Malaysia Airlines jet may have turned back)
Tom Blinken, President Barack Obama's deputy national security adviser, said on NBC's "Meet the Press" Sunday that the U.S. government is "actively looking into all questions" raised by the disappearance of the missing flight. It was on route from Kuala Lumpur to Beijing
(Read more: What is the status of the missing jet investigation?)
Flight MH370 disappeared off the Vietnamese coast on Saturday, after losing contact with air traffic controllers in the eastern Malaysia.
The flight, which operated on an 11-year old Boeing 777-200, last had contact with air traffic controllers 120 nautical miles off the east coast of the Malaysian town of Kota Bharu, or between 1-2 hours after take-off.
The aircraft, which took off at 12.40am local time on Saturday, was flying in good weather conditions and disappeared without a distress call from the crew.
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Mystery into the missing jetliner deepened after two passengers were reportedly found to have boarded the plane using stolen passports.
A passenger manifest issued by Malaysia Airlines after its plane went missing included the names of Christian Kozel, 30, from Austria, and Luigi Maraldi, 37,from Italy. However, foreign ministries of both countries confirmed the two men were not on the flight.
The development triggered speculation that the disappearance of the flight could be linked to terrorism.
A senior U.S. official told NBC News no electronic "chatter" has been detected indicating any known terror group was behind the aircraft's disappearance.
"On the possibility of a hijack, we are not ruling out any possibility. However, it is important to state that our main concern is to focus our effort on finding the missing aircraft. So by being able to find the aircraft, it will definitely help us to establish exactly what has happened," said Rahman of Malaysia's Department of Civil Aviation
"On the issue of false passports, the authorities concerned are investigating all these claims," he added. The airline's next press conference will be held on Monday at noon.
International police agency Interpol confirmed two passports recorded as lost or stolen in its database were used by passengers on board a missing Malaysia Airlines flight late Sunday, and said it was "examining additional suspect passports."
According to terrorism analysts, it is unusual, but not unheard of, for one person to board a plane with a stolen passport, and very rare for two people with stolen passports to board the same plane.
U.S. officials told NBC News on Saturday they were investigating terrorism concerns. However, there are other criminal reasons stolen passports are used to board a plane, officials said, such as drug smuggling.
"You can't rule anything out. Use of false documents is a concern, but it's an open question. It has to be followed up," said Andrew Herdman, director general, Association of Asia Pacific Airlines (AAPA).
While there has still been no sighting of the wreckage, Vietnamese rescue planes said they had spotted large oil slicks and a column of smoke off the country's coastline, Reuters reported. However, Rahman said it remains unknown whether the oil has come from the aircraft.
If it is confirmed that the plane crashed, it marks the second fatal accident involving a Boeing 777 in less than a year and by far the worst since the jet entered service in 1995. An Asiana Airlines Boeing 777-200ER crash-landed in San Francisco last July, killing three passengers and injuring more than 180.
The tragic incident, which has shaken up travelers across the world, could lead to wave of booking cancellations for Malaysia Airlines in the short-term, say industry watchers.
"It's a shock to everyone concerned. Evidence from past accidents indicates you will likely see booking cancellations. Some people will favor other airlines for a period, it's entirely natural," said Herdman.
How the carrier responds to this emergency will be critical to restoring its reputation, he added.
Malaysia Airlines has established itself as one of the Asia-Pacific's best full-service carriers in terms of safety and service.
The last fatal incident involving a Malaysia Airlines aircraft took place on September 15, 1995, when 34 people died after a Fokker 50 crashed on approach to Tawau, a town in the Eastern Malaysian state of Sabah.
—Reuters and NBC News contributed to this report