Officers were called to the property at about 5.30am on Friday morning. Police said they believe all involved in the incident were known to each other.
A teenager has been arrested on suspicion of murder after three people died in a flat in Luton, police have said.
A firearm was recovered after the incident in Leabank, off Wauluds Bank Drive, on Friday morning, Bedfordshire Police said.
Officers were called at about 5.30am following reports of concern for the welfare of people inside the flat.
Three people were found with injuries but all died at the scene, the force said.
An 18-year-old man was arrested in Bramingham Road a short time later and remains in police custody.
Bedfordshire Police said officers had recovered a firearm from Bramingham Road, and that the force believed all those involved in the incident were “known to each other”.
The force also said it believed there is no threat to the wider community. Assistant chief constable John Murphy said that “at this stage we are not looking for anybody else”
He said the three people found “had been very badly injured” and “were subsequently pronounced dead at the scene”.
An investigation is being led by the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit.
Detective Superintendent Rob Hall said: “Our thoughts are very much with the loved ones of the three people who have died in this tragic and shocking incident.”
He added: “We are still in the early stages of this investigation and formal identification of the victims has yet to take place. However, we do believe that all of those involved are known to each other and we are not currently looking for anyone else in connection to this incident.
“We’ll have officers working around the clock both at the scene and in the community over the weekend and I would encourage anyone with concerns to speak to their local community officers.”