two millionaire people traffickers have been heard mocking the migrant boat disasters that have resulted in thousands of deaths in the mediterranean , it has been reported .
one of them , an eritrean called mered medhanie , was heard laughing on a police wiretap about overloading migrant ships , a problem that causes them to capsize .
reports of the conversations come just days after at least 900 people were feared to have drowned in one of the worst maritime disasters since the end of world war two .