(CNN) -- An oil slick, the sound of a distant "ping," objects in the water, and now this: smoke spotted rising from an island in the Java Sea.
As ships, planes and helicopters scour the waters off Indonesia's coast for missing AirAsia Flight QZ8501, there have been several reports of possible signs of the missing plane.
So far, officials say, none of them have panned out.
On Tuesday, search teams will be checking the area where Indonesian navy helicopter crews saw the smoke, the head of search and rescue in the province of Bangka-Belitung told CNN Indonesia. But authorities don't know whether there's any connection to the missing jet.
Local media in Indonesia reported the smoke was seen on Long Island, one of thousands that make up the archipelago that forms Indonesia.
Searchers have been scanning the water's surface for signs of the plane, which went missing with 162 people aboard on Sunday as it flew between the islands of Belitung and Borneo, a heavily traveled shipping channel with shallow waters.
"Our early conjecture is that the plane is in the bottom of the sea," said Bambang Sulistyo, the head of Indonesia's search-and-rescue agency. That belief is based on the plane's flight track and last known coordinates, he said.
Several possible signs of the missing plane, including an oil slick within the search zone and the sound of a faint "ping," have been discounted, according to Indonesian authorities, who are heading the search.
Indonesia Vice President Jusuf Kalla said there were "some reports from Australia" about possible objects found, but it was unclear whether they were from the plane.
Because there is a great deal of traffic along the water in the search area, authorities have cautioned that objects found might have nothing to do with the missing aircraft.
Rescuers say weather was probably a factor in the plane's disappearance, and it has made finding traces of the plane more difficult.
Large waves and clouds hampered the search for the plane on Sunday and Monday.
"It is not easy, of course ... the operation in the sea, especially in the bad weather like this," Kalla said.
But Kalla said his country will not give up or set a time limit for the operation.
The search area is expanding, with six zones added to the operation on Tuesday, Sulistyo told reporters.
Now, he said, teams in the air, on sea and on land are searching 13 zones over an area that stretches about 156,000 square kilometers (60,200 square miles).
Report: Higher altitude request denied
AirAsia says air traffic controllers lost contact with the aircraft at 7:24 a.m. Sunday, Singapore time (6:24 a.m. in Indonesia).
The plane, flying from the Indonesian city of Surabaya to Singapore, went missing as it flew over the Java Sea between the islands of Belitung and Borneo -- a heavily traveled shipping channel with shallow waters -- Indonesian authorities said.
Before the plane, an Airbus A320-200, lost contact with air traffic controllers, one of the pilots asked to change course and fly at a higher altitude because of bad weather, officials said. Heavy thunderstorms were reported in the area at the time.
Air traffic control approved the pilot's request to turn left but denied permission for the plane to climb to 38,000 feet from 32,000 feet, Djoko Murjatmodjo, an aviation official at the Indonesian Transport Ministry, told the national newspaper Kompas.
The increased altitude request was denied because there was another plane flying at that height, he said.
Djoko suggested that Flight 8501 ascended despite air traffic control denying it permission.
AirAsia CEO Tony Fernandes said storm clouds caused the pilot to ask for a flight plan change. But he added, "We don't want to speculate whether weather was a factor. We really don't know."
Once the aircraft is found, there will be a proper investigation, Fernandes said.
Relatives to be flown over search area
Amid the anxious wait, family members of the passengers have attended closed-door briefings with airport and airline officials at the airport in Surabaya.
Oei Endang Sulsilowati and her daughter were looking for information about her brother, his wife and their two children.
"We don't know what to do," Sulsilowati said. "We are just waiting for news."
A specially chartered plane will fly relatives of passengers over the search area Wednesday, AirAsia Indonesia CEO Sunu Widjatmoko told reporters in Surabaya on Tuesday.
The chartered Airbus A320 that will take families from Surabaya over the zone has room for as many as 180 people, he said.
Some police said authorities were seeking additional materials to help identify passengers, such as photos with close-ups of teeth, DNA, or fingerprints. But police officials later told CNN they were not immediately seeking these materials.
East Java Police have set up a disaster victims identification area at the Surabaya airport.
Of the people on board the passenger jet, 155 are Indonesian, three are South Korean, one is British, one is French, one is Malaysian and one is Singaporean, the airline said.
Eighteen children, including one infant, are among the passengers, the carrier said. Seven of the people on board are crew members.
International search team
Since the flight disappeared in Indonesian airspace, Indonesia is heading up search efforts.
More than 1,100 search and rescue personnel from Australia, Singapore, Malaysia, South Korea, Japan and New Zealand are joining the search alongside Indonesia's teams, CNN Indonesia reported.
The missing plane is made by Airbus, a French company. And France has dispatched two investigators to Indonesia. They are due to arrive in Jakarta on Monday, France's Foreign Ministry said.
Malaysia's transportation minister said his country has deployed three vessels and three aircraft to assist in the search. And the Royal Australian Air Force said Monday that it was deploying a patrol plane to help.
The USS Sampson is on its way to the Java Sea to assist in the search for the missing AirAsia plane, a senior U.S. military official told CNN Chief National Security Correspondent Jim Sciutto. The Sampson, a guided-missile destroyer based in San Diego, deployed in October to take part in "maritime security exercises and training" in the Pacific.
China will dispatch aircraft and ships to participate in search and rescue efforts, the Chinese Ministry of National Defense said Tuesday.
The MH370 mystery
AirAsia, a successful budget airline group headquartered in Malaysia, had a clean safety record until the disappearance of Flight 8501. The missing plane is operated by the company's Indonesian affiliate.
The loss of contact with the plane comes nearly 10 months after the disappearance of Malaysia Airlines Flight 370, which dropped off radar over Southeast Asia on March 8 with 239 people on board.
Searchers have yet to find any remains of Flight 370, which officials believe went down in the southern Indian Ocean after mysteriously flying thousands of kilometers away from its planned route from Kuala Lumpur to Beijing.
But some aviation experts don't think the search for Flight 8501 will be as challenging as the hunt for MH370.
"We are not talking about the deep Indian Ocean here," CNN aviation correspondent Richard Quest said. "We are talking about congested airspace around Southeast Asia. There will be much better radar coverage. There's certainly better air traffic control coverage."
CNN's Susanna Capelouto, Andrew Stevens, Paula Hancocks and Lucia Isman contributed to this report. Azieza Uhnavy also contributed to this report.