Alien experts accuse NASA of hiding underground bases on Mars. Based on images taken by NASA, UFO investigators claim that mysterious figures and structures in the planet were constructed by aliens to hide their presence.

A video uploaded on YouTube shows various images from Google Earth with certain regions in the red planet that alien enthusiast Sandra Elena Andrade claims to be structures built to house aliens.

Some sources say that the structures were originally discovered by Marcelo Irazusta, a Mars anomaly hunter, who found at least seven cryptic structures formed like entrances scattered around Mars.

Alien hunters believe that some of the structures were intentionally hidden by a 'crappy Photoshop job'.

"Mysterious structures on Mars, most are intentionally hidden. The new discoveries that gives the researcher Marcelo Irazusta coordinates," Andrade wrote in the description of the video entitled, "Sensational Discovery: Martian City?"

The video uploaded on Dec. 2, has 82,599 views and UFO enthusiasts commented on odd-looking black holes that Andrade claims to be entrances into underground alien bases.

"Look closely and you will see the edges of an entrance that takes ships below the surface of Mars," Scott C. Waring, a UFO investigator said.

"This is the location Earth should choose if they want to make a settlement on Mars. This is a location that's already been used and proven effective by aliens. It's probably abandoned...just waiting for new owners," he added.

Meanwhile, another YouTube user, DAHBOO77, posted a video of the same mysterious entrance-looking structures on Mars.

"After doing some searching, I discovered many of these entrances. At this point it's rather obvious that there was at least intelligent life on mars in the past," the user posted.

"These are of the secrets they are keeping from the masses! The only way you're going to find the truth is to go digging and looking for it! Don't be fooled by the coming Deception! Stay tuned for more! Eyes to the Skies!" he added.

There are some people who were not convinced that these figures pertain to alien structures. A user named WhatsUpInTheSky37 says that the structures are not entrances but they are caused by Google Earth algorithm lining on the globe.

"If you notice they all occur along the line where two images meet. The top one is darker and has a better resolution to the bottom image. You cannot rely on anything you see on Google Earth for true anomaly hunting," he commented.