Freda Walker, 86, and her 88-year-old husband Kenneth were found at their home in Station Road by a concerned neighbour at 9am on Saturday.
Freda was pronounced dead at the scene while Keneth was rushed to hospital where he remains in a critical condition with life-threatening injuries.
Detectives have been trawling CCTV and conducting house-to-house enquiries to find those responsible in the days since.
Derbyshire’s Assistant Chief Constable Dave Kirby said: “Since Saturday a team of officers have been working round-the-clock to bring those responsible for this horrific crime to justice.
“Hours of CCTV footage has been downloaded and is being viewed – and it is clear from the images that there are a number of people who walk or drive along Station Road between 4.30pm on Friday and 9am on Saturday.
“If you know you were in that street between those times, I urge you to contact the force immediately so officers can ensure that any information is captured – and that you can be discounted from any enquiries.”
Officers have also been working to understand the times when the couple were last seen alive – and believe that Freda was last spoken to at around 6.40pm on that Friday evening.
Assistant Chief Con Kirby said: “We know that Freda visited a neighbour in the late afternoon, leaving the house at around 4.55pm.
“She walked back to her home and then was spoken to at 6.40pm. The next time she was seen by anyone outside of her house was when she was found dead the next morning.
“Officers need to speak to anyone who may have spoken to or seen Freda or Keneth after that time on Friday evening.”
Anyone who may be able to help detectives with their enquiries should contact Derbyshire police using any of the below methods, including reference 240-150122.
Facebook – send a private message to /DerbyshireConstabulary
Twitter – direct message the force’s contact centre on @DerPolContact
Website – complete the contact form at www.derbyshire.police.uk/ContactUs
Phone – call 101
You can also anonymously contact Crimestoppers on 0800 555 111.