The royal palace has fired the four bodyguards of the former king, queen and crown prince who died of gunshots in the massacre on June 1st.
The guards - and two orderlies who worked for the prince who is accused of killing his family and then himself - have been sacked.
A government-appointed inquiry team has announced that Crown Prince Dipendra, drunk and high on hashish, had killed his parents, King Birendra and Queen Aiswarya, and seven other royals during a dinner on June 1 at the palace.
The report said Prince Dipendra's bodyguards told the investigators they knew about his drug habits, but did not report about it to anyone and instead helped him obtain drugs.
The report said Prince Dipendra had asked an aide for cigarettes laced with hashish and another unidentified black substance just before the shooting. The investigators were told by one of the prince's aides that Prince Dipendra had been smoking such cigarettes for a year.
Eyewitnesses of the massacre told government investigators the prince went on the rampage because of his parents' opposition to his choice of bride.
Palace officials also said they are reviewing the entire security arrangements at the royal palace.