A bizarre shape that was photographed soaring through the sky in China remains a mystery, with government officials failing to provide any official comment on the issue.
The UFO, which was described by some as looking like a "fireball", spooked locals and forced a major Chinese airport to ground several flights to avoid a collision.
The government has not yet given an official explanation for the incident, apart from one unnamed source telling the China Daily that it had a "military connection".
Staff at Xiaoshan International Airport in south-east China reportedly saw the bright light twinkling in the sky last Friday, leading them to declare a security risk and shut down operations.
Eighteen flights were affected during the incident and the airport re-opened one hour later when the object was no longer visible.
One unverified image that was purportedly taken by locals during the incident and has been circulating in the Chinese press shows a train-like object with two long strips of lights along its side in the sky. But UFO enthusiasts have hit out at the authenticity of this photo, saying it bears a striking similarity to long-exposure photographs taken of helicopters.
"I don't think a helicopter is what was witnessed," wrote one commentator on the forum Above Top Secret.
"I do, however think that it is definitely a helicopter in this picture and is more than likely unrelated to the incident."