Local vibrations of oxygen in Ge crystals grown from a melt fully covered by B2O3 were evaluated by Fourier-transform infrared spectroscopy. Ge single crystals containing oxygen were grown by the Czochralski method under various growth conditions. Oxygen concentrations in the crystals were determined to be in the range between 8.5 × 1015 and 5.5 × 1017 cm-3 from the infrared absorption at 855 cm-1 originating in local vibration of Ge-Oi-Ge quasi-molecules. Absorption peaks relating to GeOx, SiOx and Si-Oi-Si were not detected in the as-grown crystals. The calibration coefficient for determining oxygen concentration in Ge crystals from the absorption peak intensity at 1264 cm-1 was estimated to be 1.15 × 1019 cm-2.