GRB 100614A (upper panel) and GRB 100615A (bottom panel) X-ray lightcurves, together with all the optical/NIR upper limits estimated using several ground-based facilities (see Table 1 for details). Cyan, blue, magenta, green, yellow, black and red upper limits represents the g′ (and all those bands bluer than g′), R, I, z, J, H, K bands, respectively. Vertical dashed lines emphasize the reddest observations and the time at which they have been obtained. Such observations are used in our analysis. The faintest X-ray data in the bottom panel draws the GRB 100615A Chandra observation (Butler et al. 2010).