The present invention relates to yarns, fibres or filaments made of thermoplastics and to their manufacture. It relates more particularly to yarns, fibres or filaments exhibiting good fire resistance properties and to processes for the manufacture of these articles. These yarns or fibres made of polymer are obtained by spinning a polymer comprising an additive possessing flame-retardant properties composed of at least particles of a solid substrate on which a flame-retardant compound is adsorbed.