Detectives were today questioning a number of people after two bodies were discovered in a car boot.
The victims - a man and a woman - were found in a blue Ford Mondeo at an address in Kensington Way, in Holbeck, Leeds, early yesterday morning.
A West Yorkshire Police spokesman said a number of people had been arrested in connection with the investigation and were being held at police stations across the county.
Post-mortem examinations were due to be carried out on the bodies yesterday.
Neighbour Alex Smith told reporters he saw people loading up the car outside the house in the early hours of Sunday morning.
He said: "I was woken up at about 12 o'clock this morning and I heard the police shouting. They arrested two young people that lived next door, a man and a woman.
"The girl and the guy were just sat out on the curb and they were handcuffed together. The guy said 'what have I been arrested for?' and the officer said something to do with the murder of someone.
"Over the past two days there has been something going on because they have kept going in and out of the garage and there has been lots of banging in the early hours of the morning.
"At about 5am or 5.30am on Sunday morning I looked out of the window and they were taking stuff from the garage and putting it in to the car and I thought 'well that's a bit early to be doing that'.
"I saw them put a quilt cover and pillow in to the car but then they were reversing the car back in to the garage. They were putting stuff into the boot.
"My wife said they were trying to put the bin out and the woman was really struggling. A man came out to help her and they had to lift it out together. I knew there was something going on but I thought it was to do with drugs."
Mr Smith, a clinical support worker for the NHS, told the Daily Mail: "There are about five or six people who live in the house and they are all of Chinese origin.
"The majority of them are male and they come and go, but there is one female who has been there since I moved in nearly two years ago."
He said some of the people living in the rented house worked at a nearby Chinese restaurant.