Rescue helicopters and ships searching for a Malaysia Airlines jet rushed Monday to investigate a yellow object that looked like a life raft. It turned out to be moss-covered trash floating in the ocean, once again dashing hopes after more than two days of fruitless search for the plane that disappeared en route to Beijing with 239 people on board.

With no confirmation that the Boeing 777 had crashed, hundreds of distraught relatives waited anxiously for any news. Thai police and Interpol questioned the proprietors of a travel agency in the resort town of Pattaya that sold one-way tickets to two men now known to have been traveling on flight MH370 using stolen passports.

Malaysia’s Department of Civil Aviation chief, Azharuddin Abdul Rahman, told a news conference that investigators were looking at “every angle” to explain the plane’s disappearance early Saturday, including hijacking.

“There are many experts around the world who have contributed their knowhow and knowledge,” Azharuddin said. “As far as we are concerned, we are equally puzzled as well.”

The search operation has involved 34 aircraft and 40 ships from several countries covering a 50-nautical mile radius from the point the plane vanished from radar screens between Malaysia and Vietnam, he said.

Experts say possible causes of the apparent crash include an explosion, catastrophic engine failure, terrorist attack, extreme turbulence, or pilot error or even suicide.

Selamat Omar, a Malaysian whose 29-year-old son Mohamad Khairul Amri Selamat was a passenger on the flight, expected a call from him at the 6.30 a.m. arrival time. Instead he got a call from the airline to say the plane was missing.

“We accept God’s will. Whether he is found alive or dead, we surrender to Allah,” Selamat said.

There have been a few glimmers of hope, but so far no trace of the plane has been found.

On Sunday afternoon, a Vietnamese plane spotted a rectangular object that was thought to be one of the missing plane’s doors, but ships working through the night could not locate it. Then on Monday, a Singaporean search plane spotted a yellow object some 140 kilometers (87 miles) southwest of Tho Chu island, but it turned out to be some sea trash.

Malaysian maritime officials found some oil slicks in the South China Sea and have sent a sample to a lab to see if it came from the plane.

As relatives of the 239 people on the flight grappled with fading hope, attention focused on how two passengers managed to board the aircraft using stolen passports. Interpol confirmed it knew about the stolen passports but said no authorities checked its vast databases on stolen documents before the jet departed.

Warning that “only a handful of countries” routinely make such checks, Interpol secretary general Ronald Noble chided authorities for “waiting for a tragedy to put prudent security measures in place at borders and boarding gates.”

There was no indication that the two men had anything to do with the tragedy, but the thefts of the passports added a twist to the plane’s mysterious disappearance, fueling speculation of foul play, terrorism or a hijacking gone wrong.

The two stolen passports, one belonging to Austrian Christian Kozel and the other to Luigi Maraldi of Italy, were entered into Interpol’s database after they were stolen in Thailand in 2012 and last year, the police body said.

Electronic booking records show that one-way tickets with those names were issued Thursday from a travel agency in the beach resort of Pattaya in eastern Thailand.

Thai police Col. Supachai Phuykaeokam said those reservations were placed with the agency by a second travel agency in Pattaya, which told police it had received the bookings from a China Southern Airlines office in Bangkok.

The owners of the second Pattaya travel agency refused to talk to reporters. Thai police and Interpol officers went in to question the owners.

Malaysian Transport Minister Hishammuddin Hussein said Sunday that officials have footage of the two men, and were examining it. He said local and international intelligence agencies were involved in the investigation.

A telephone operator on a China-based KLM hotline confirmed Sunday that passengers named Maraldi and Kozel had been booked on one-way tickets on the same KLM flight, flying from Beijing to Amsterdam on Saturday. Maraldi was to fly on to Copenhagen, Denmark, and Kozel to Frankfurt, Germany.

As holders of EU passports with onward flights to Europe, the passengers would not have needed visas for China.

Interpol said it and national investigators were working to determine the true identities of those who used the stolen passports to board the flight.

Interpol has long sounded the alarm that growing international travel has underpinned a new market for identity theft: Bogus passports are mostly used by illegal immigrants, but also pretty much anyone looking to travel unnoticed such as drug runners or terrorists. More than 1 billion times last year, travelers boarded planes without their passports being checked against Interpol’s database of 40 million stolen or lost travel documents, the police agency said.

Azharuddin also said the baggage of five passengers who had checked in to the flight but did not board the plane were removed before it departed, he said. Airport security was strict according to international standards, surveillance has been done and the airport has been audited, he said.

(AP)