Airbus FCOM:
"Note: Expect the SMOKE warning to remain after agent discharge, even if the smoke source is extinguished. Gases from the smoke source are not evacuated, and smoke detectors are also sensitive to the extinguishing agent."
Airbus FCTM:
"The crew should be aware that, even after successful operation of the cargo fire bottle, the CARGO SMOKE warning might persist due to the smoke detectors being sensitive to the extinguishing agent."