The two men were arrested and questioned at Holborn police station in central London following the death of a man from multiple wounds following a struggle at the men's flat.
Both men were released on bail until 6 March while detectives conduct their inquiries.
The latest incident comes as the Crown Prosecution Service is still deciding whether to press charges over the death of Robert Ingham, 22, who died when he was involved in a fight with Nick Baungartner, 53, at his home in Ockbrook, Derbyshire.
After the struggle both men ended up in hospital, where Mr Ingham later died. Mr Baungartner, who runs a business laying tennis courts, was treated for a broken wrist, heavy bruising and shock. However, in the wake of that death and concern over a number of other incidents, it emerged that police forces are shortly to be told not to rush into prosecutions against those who hit out in self-defence.
The most recent death, of Brian Firmager, 32, from Bromley, south-east London, is bound to add intensity to the debate sparked by Michael Howard, the Home Secretary, when he expressed concern that the victim often appeared to be treated more harshly than the villain.
Mr Firmager died from stab wounds just four hours after staggering into Guy's hospital, central London, at 1.30am last Thursday. Detectives later discovered that the dead man had been involved in an incident with two men at their flat in an apartment block near Hatton Garden, central London.
t Tony Garrard, 34, from Lee in south-east London, appeared at Clerkenwell magistrates' court, central London, at the weekend, charged with aggravated burglary.