Investigations of runaway electrons (REs) during induced disruptions are performed at the TEXTOR tokamak. The synchrotron radiation generated by REs in the plasma core is detected using an infrared camera. The measurements enable the observation of the structure and dynamics of the runaway beam. In particular, the runaway beam is investigated as a function of the vertical and horizontal control fields. From the plasma current a runaway number of 4.33 × 1016 was calculated. The number of REs with energies exceeding 25 MeV is 6.4 × 1015 according to the synchrotron measurement at the end of the current quench phase. The mean pitch angle of the >25 MeV runaways is found to be 52 mrad which is smaller than in the low density discharge scenario. In addition, the synchrotron measurements show for the first time that a significant number of the high energy REs can survive after the end of the current plateau phase. In order to understand this, runaway orbit calculations have been performed which are in good agreement with the measurements.