In 1990, it was reported that several Sri Lankan lawyers, Members of parliament and trade unionist who regularly enquired on behalf of lawyers and students who had disappeared in Sri Lanka had received anonymous telephone calls warning them not to pursue their enquiries. The drastic drop in habeas corpus petition on behalf of disappeared persons was attributed to killing by vigilante groups of three lawyers who had filed over 400 cases in respect of persons missing in the south the country. Other threatened persons were journalists, dramatists, free-lance writers, trade unionists, human rights workers, social workers, and most recently those released from detention camps.