The Restricted Zone is an area within the Biologic Space Labs Research Station. The Restricted Zone is a high-security level area designed with the sole purpose of Metroid breeding and research within the Restricted Laboratory.
The Restricted Zone hides behind a large lock that can only be opened by one side, presumably an inside worker would allow an outside incomer provided he or she was authorized. Samus opens the lock using the Wave Beam, penetrating through walls to reach the switch. Once inside, all hatches within the zone are Level 4 Locks, the highest locks available on the station.
- Main article: Restricted Laboratory
The small area is home to only one Save Station, the Restricted Laboratory, and very few other rooms. There are no enemies in the Zone. Though as Samus enters the Restricted Laboratory, there are Metroids which do not attack Samus. SA-X also enters the area, releasing the creatures, but is quickly destroyed by Metroids. After the SA-X is destroyed and Samus retreats away from the Restricted Laboratory, the entire Laboratory detaches itself from the Restricted Zone.
The Restricted Zone houses only one Power Bomb Expansion. This can only be obtained on a second visit to the Restricted Zone. Returning to where the Restricted Laboratory detached itself, Samus can use the Speed Booster to Shinespark her way through Speed Booster Blocks to a Power Bomb Expansion.
- The background of the Zone has typed writing saying "Level X" and large letters "L-X" on it.
An SA-X being attacked by Metroids in the Restricted Laboratory
- "As you can see, the Federation has been secretly working on a Metroid breeding program. For peaceful application only, of course. Please understand. But perhaps you already knew of this program's existence? Certainly, you must have had doubts when you saw Sector 1. SRX, a faithful replica of the SR388 ecosystem... Ideal for raising Alpha, Gamma, Zeta, and even Omega Metroids. This research even uncovered techniques for rapid growth. Imagine...creating an Omega from a larval Metroid in days... But that research is finished. The X has smelled out its natural enemy, and one of the SA-X is on its way here..." —Adam Malkovich (Metroid Fusion)
- "Warning. No entry without authorization." —Security Computer Voice (Metroid Fusion)