A police officer confirmed the arrests but declined to give further details.
Police sources, however, said that the arrested include two students of a prominent college of Noida.
Sarna, 21, died in a hospital where he was taken after being found unconscious in a pool of blood outside a residential complex in south Delhi where he was partying at his friend's flat Sep 13.
He was allegedly beaten up by two security guards when he created ruckus after taking a drug overdose at the party. His autopsy said he died due to shock and haemorrhage caused by head injuries. There were major injuries on his private parts also.
The two guards are now in custody, along with the four friends, who were arrested under the Narcotic Drugs and Psychotropic Substances Act.
Sarna's family, who have reached Delhi from their home in the US, have demanded a Central Bureau of Investigation inquiry into his alleged murder.
--IANS (Posted on 20-09-2013)