Officers were called to the junction of Broom Way and Spitfire Way, Lee-on-the-Solent, in the early hours of Thursday, October 7 after the man became unwell.
An ambulance took him to Queen Alexandra Hospital where he died.
A spokesman for Hampshire police said: ‘Police were called at around 1am on Thursday, October 7 by the ambulance service after a man in his 40s had become unwell at the junction of Broom Way and Spitfire Way, Lee-on-the-Solent.
‘The man was transported to QA Hospital where he subsequently died.
‘Enquiries remain ongoing to establish the cause of the death, however it is deemed suspicious at this time and officers have made two arrests as part of the investigation.
‘A 35-year-old man from London and a 26-year-old man from Essex have been arrested on suspicion of conspiracy to commit murder.
‘They have been bailed until 4 November while enquiries continue.’
A spokeswoman for the South Central Ambulance Service (SCAS) added: ‘SCAS were called at 12.33am (October 7) to Spitfire Way to a medical emergency. We sent to the scene two ambulance crews and an ambulance officer, in addition to another off duty ambulance officer who had come across the situation.
‘They were assessing and treating one patient who was in a life-threatening condition. Following assessment and treatment at the scene by all our crews the patient was taken to the Queen Alexandra Hospital.’