KUALA LUMPUR/PHU QUOC ISLAND, Vietnam, March 10 -- The international massive search for the missing Malaysia Airlines plane continued Monday, but no solid clues have been found yet.

Vietnamese airborne searchers reportedly spotted an object on Sunday floating at the area where the Boeing 777 aircraft suddenly vanished from radar screens and suspected it to be a door of the ill-fated plane.

"From this object, hopefully (we) will find the missing plane," state-run Thanh Nien daily quoted Lt. Gen. Vo Van Tuan, deputy chief of staff of the Vietnamese army, as saying.

However, till Monday noon searching ships have failed to locate the item.

According to the Malaysian Department of Civil Aviation, search and rescue teams from Australia, China, Thailand, Indonesia, Singapore, Vietnam, the Philippines and the United States have joined the hunt.

Chinese warship Mianyang arrived at the waters on Monday morning three hours ahead of schedule, and it started searching operations upon its arrival.

Also on Monday morning, a Chinese governmental work group left Beijing for Kuala Lumpur. "The most pressing and important work remains search and rescue," said Guo Shaochun, head of the group.

A team of experts from the U.S. National Transportation Safety Board, the Federal Aviation Administration and Boeing were also expected to arrive at Kuala Lumpur on Monday.

Meanwhile, Malaysian authorities expect to complete by Monday afternoon a lab analysis of the samples collected from an oil slick at the suspected waters. The oil has triggered speculations that the plane might have crashed nearby.

In parallel with the intensive hunt for the missing plane, which was carrying 227 passengers and 12 crew members from Kuala Lumpur to Beijing, investigation into the use of stole passports has also picked up steam.

Interpol on Sunday confirmed that at least two stolen passports were used by unidentified passengers on the plane, adding that the agency is investigating more suspicious passports involved.

On Saturday, Italian and Austrian authorities confirmed that passports of Christian Kozel and Luigi Maraldi, whose names were listed in the MH370 manifest, had both been stolen in Thailand.

The theft was registered in Interpol's database, which is only available to law enforcement authorities. And "few member countries have systematically searched Interpol's databases," said the agency.

Malaysia's state news agency, Bernama, quoted Home Minister Ahmad Zahid Hamidi as saying that the passengers using the stolen European passports were of Asian appearance.

"I am still perturbed. Can't these immigration officials think? Italian and Austrian (passport holders) but with Asian faces," he was quoted as saying late Sunday.

Although it is too soon to speculate about any connection between these stolen passports and the missing plane, said Interpol's secretary-general, Ronald Noble, "it is clearly of great concern that any passenger was able to board an international flight using a stolen passport listed in Interpol's databases."

In Thailand, a senior police officer said Sunday that authorities were probing a passport racket on the resort island of Phuket, where Maraldi's passport was stolen.