  Using the data on magnetic field maps and continuum intensity for Solar
Cycles 23 and 24, we explored 100 active regions (ARs) that produced M5.0 or
stronger flares. We focus on the presence/absence of the emergence of magnetic
flux in these ARs 2-3 days before the strong flare onset. We found that 29 ARs
in the sample emerged monotonously amidst quiet-Sun. A major emergence of a new
magnetic flux within pre-existing AR yielding the formation of a complex
flare-productive configuration was observed in another 24 cases. For 30 ARs, an
insignificant (in terms of the total magnetic flux of pre-existing AR)
emergence of a new magnetic flux within the pre-existing magnetic configuration
was observed; for some of them the emergence resulted in a formation of a
configuration with a small $\delta$-sunspot. 11 out of 100 ARs exhibited no
signatures of magnetic flux emergence during the entire interval of
observation. In 6 cases the emergence was in progress when the AR appeared on
the Eastern limb, so that the classification and timing of emergence were not
possible. We conclude that the recent flux emergence is not a necessary and/or
sufficient condition for strong flaring of an AR. The flux emergence rate of
analyzed here flare-productive ARs was compared with that of flare-quiet ARs
analyzed in our previous studies. We revealed that the flare-productive ARs
tend to display faster emergence than the flare-quiet ones do.
