Many authors (Haunschild et al., Phys. Status Solidi RRL 5, 199-201 (2012) [1]) reported about areas in Cz-Si with an extremely low lifetime of minority carriers after high temperature stages of solar cell manufacture. In such regions the minority carrier lifetime may be fallen 100 times after annealing, what leads to a considerable drop in the solar cell efficiency. In present work the electrical and structural properties of phosphorus doped Bosch Cz-Si wafers with degrading areas were studied by means of photoluminescence, deep level transient spectroscopy, transmission electron microscopy, electron energy loss spectroscopy and Fourier transform infrared spectroscopy. Based on these data it is concluded that the dominant recombination channel in the degrading areas is related to strained oxygen precipitates. We found electronic states of traps which may cause their formation.