Post-mortem examinations on two men found dead in a back garden will be carried out later on Saturday, investigating officers have said.
Humberside Police said the deaths in May Street, Hull, were being treated as "suspicious but unexplained".
Officers were called to the terraced street on Friday evening and a cordon was still in place on Saturday morning.
Police will search through CCTV and use forensic specialists to find out more about what happened.
The men have not formally been identified and police will be deploying specialist officers to support their families, a force spokesman said.
He said post-mortem examinations will be held later to establish the cause of death of both men.
Detective Superintendent Matt Hutchinson said: "Unsurprisingly, this incident will be of great concern to the local community and, as a result, extra officers will be in the May Street area carrying out enquiries and reassuring the public.
"Significant enquiries are under way to establish how and when the men died.
"A large number of police resources are working on the investigation carrying out house to house, CCTV and forensic enquiries.
"We still need the public's help and I would urge anyone with information about the deaths to call Humberside Police immediately as your call could make a big difference to the investigation.
"We would especially like to speak to those people who have been living or visiting 7 May Street over the last week.
"We need their help to assist in establishing the movements to and from the address."
Anyone with information is asked to call 101.