The United Kingdom shut down the UFO unit of its Ministry of Defense (MoD) four years ago and now has released all documents about extra-terrestrial encounters, AFP.com reported.

The documents showed no real threats to the U.K. and concluded that extra terrestrials were not likely to exist. The MoD closed its UFO hotline in 2009 after receiving record-high calls. Many people reportedly confused alien space ships for Chinese lanterns, popular at weddings and parties.

Civil servant Carl Mantell told Bob Ainsworth, the defense minister at the time, that the UFO unit staff was exhausting all of its increased work time, but had no valuable output.

"No UFO sighting reported to (MoD) has ever revealed anything to suggest an extra-terrestrial presence or military threat to the UK," he wrote in a memo. "The level of resources diverted to this task is increasing in response to a recent upsurge in reported sightings, diverting staff from more valuable defense-related activities."

The recently released files reveal that from 2000 to 2007, an average of 150 tips were received per year. Sightings included locations like Stonehenge and the House of Parliament. In the eleven months leading up to its disbanding, the hotline received 520 tips.

Officials said the likely cause of the spike in tips was due to a growing trend of releasing Chinese lanterns into the air for wedding celebrations and other parties. Dr. David Clarke, a Sheffield Hallam academic and the National Archives consultant on the UFO files, said about two-thirds of the sightings reported were likely the lanterns, the Telegraph reported.

"The last pieces of the puzzle have finally been revealed with this insight into the last days of the UFO desk," Clarke said. "The last files from the UFO desk are now all in the public domain. People at home can read them and draw their own conclusions about whether 'the truth' is in these files or still out there."