Aviation officials in Pakistan, India and Central Asia as well as Taliban militants said they knew nothing about the whereabouts of a missing Malaysian jetliner on Monday after the search for Flight MH370 extended into their territory.
Malaysia said it had sent diplomatic notes to all countries along an arc of northern and southern search corridors including India and Pakistan, requesting radar and satellite information as well as land, sea and air search operations.
Indian defence officials rejected the possibility of a plane flying for hours above the country undetected.
"The idea that the plane flew through Indian airspace for several hours without anyone noticing is bizarre," a defence ministry official said, speaking on condition of anonymity.
"These are wild reports, without any basis," he said, adding a pilot would have to know the precise location of all Indian radars and surveillance systems to be able to get around them.
Explaining why this was unlikely, he said surveillance was so tight on India's border facing its nuclear arch-rival Pakistan that the air force scrambled a pair of Sukhoi fighters last month after an unidentified object showed up on the radar.
It turned out to be a weather balloon drifting towards the Pakistan border.
Pakistani officials said they had detected nothing suspicious in the skies after the plane vanished.
"We have checked the radar recording for the period but found no clue about the ill-fated flight," the Civil Aviation Authority said in a statement.
Central Asian countries Kazakhstan and Kyrgyzstan, at the northern end of the search arc, said no unidentified planes had entered their air space on March 8.
"Even if all on-board equipment is switched off, it is impossible to fly through in a silent mode," the Kazakh Civil Aviation Committee said in a statement sent to Reuters. "There are also military bodies monitoring the country's air space."
As the search widened, some observers suggested the plane might have flown to remote mountainous areas abutting Pakistan's border with Afghanistan where Taliban militants are holed up.
Zabihullah Mujahid, a spokesman for the Taliban in Afghanistan, who are seeking to oust foreign troops and set up an Islamic state, said the missing plane had nothing to do with them.
"It happened outside Afghanistan and you can see that even countries with very advanced equipment and facilities cannot figure out where it went," he said. "So we also do not have any information as it is an external issue."
A commander with the Pakistani Taliban, a separate entity fighting the Pakistani government, said the fragmented group could only dream about such an operation.
"We wish we had an opportunity to hijack such a plane," he told Reuters by telephone from the lawless North Waziristan region.
In Delhi, the defence official said that theoretically the aircraft could have flown a path hugging close to the Himalayas where radar is less effective because of the mountains.
But again for that sort of "terrain masking", you'd need intelligence and the skills of a military pilot, he said.
In Port Blair, capital of the remote, forested Andaman and Nicobar Islands, the Indian Navy Ship Kesari returned to its base after being recalled following a two-day search scanning the Andaman Sea.
A senior defence source there said that if the plane had crashed in the area light debris could have drifted a vast distance.
"I would estimate that debris would be travelling at least 15 nautical miles an hour, so you can imagine how far it would be after more than a week," he said.