Stranger Things stars Maya Hawke, Joe Keery and Gaten Matarazzo mask up as they film season four... amid mysterious new teaser release 

Stranger Things stars Maya Hawke, Joe Keery and Gaten Matarazzo were back throwing themselves into character on the set of their hit Netflix series on Tuesday. 

The trio were spotted filming season four at Hawkins High School, where a police car, military truck and tent sat mysteriously outside.  

Following safety precautions, all three of the stars wore face masks in between takes of the award-winning sci-fi show.

The stars appeared to already be dressed in character as they waited for their cue.

Joe, 29, wore a blue sweater, jeans, and white Nike trainers, while costar Maya, 22, sported suspenders over a plaid top.

Gaten, 18, sported an unbuttoned shirt over a long-sleeve top and belted slacks.

In addition to their eighties apparel, photos showed all the action yet to unfold in the upcoming fourth season.   

Parked outside of Hawkins High School was a school bus, a Hawkins Police Department car, and a military Jeep.

A military tent was also set up outside the school.

The new photos come amid the release of a new Stranger Things teaser posted to YouTube, entitled 'HNL Control Room.'

Set to French opera music, the eerie teaser focuses on six different monitors, all playing static. 

As the video progresses, however, mysterious images briefly flicker on each screen, including a blood-stained magic eight ball and game of chess. 

The description promised news coming soon: 'Due to technical difficulties, Hawkins National Laboratory will be closed until further notice. We will be back in service tomorrow at 9:00AM ET.'

Stranger Things fans took to the comments section and social media to speculate on what was to come.  

So far, a release date for season four has yet to be announced. 

Since 2016, Stranger Things has been mesmerizing viewers with the story of a mysterious young girl, her friends, and the supernatural forces up against them.