The Terikof Belt was an area within the Badlands. Several asteroids were M class. (VOY episode: "Caretaker")
The asteroid belt surrounded the Moriya system. (TNG novel: The Badlands, Part II)
Cardassian mining interests were established in the asteroid belt, but were finally abandoned in 2369. (TNG novel: The Badlands, Book Two, VOY novel: The Badlands, Part III)
The Maquis established a base within the Terikof Belt and in order to calculate which asteroids posed an imminent threat, a computer core was stolen. (VOY novel: The Badlands, Part III)
Starfleet discovered the Maquis base in the Terikof Belt in 2373 and removed the computer core. (DS9 novel: The Badlands, Part IV)