Either in the late 80 or early 90s I watched a sci-fi/ horror film based around 3 aliens/humanoids monitored in stasus tubes by scientists. Something happens and the tubes lose power, the aliens escape and start killing the scientists and other staff. I am sure there were 2 men and 1 women or it might have been the other way round.

Now I thought the title had "shadow" or "dark" in it but I have not come across any movie info that reads like I remember it.

Any help would be greatly appreciated :) Thanks.