Complex sentence: Over half of 142 voyages were stopped by British patrols, and most intercepted immigrants were sent to internment camps in Cyprus, the Atlit detention camp in Palestine, and to Mauritius.
Split into simpler sentences: Over half of 142 voyages were stopped by British patrols, and most of the intercepted immigrants were sent to internment camps in Cyprus. Some were sent to the Atlit detention camp in Palestine, and some to Mauritius.