Madsen is currently in custody on a charge of manslaughter until September 5. The new charges will be filed on or before that date.
Buch-Jepsen also plans to request a mental evaluation of the suspect.
Wall, 30, had boarded a 17-meter submarine built by Madsen on August 10 for a story and was last seen on that day in an image that allegedly showed her standing with Madsen in the tower of the submarine in Copenhagen Harbor.
Møller Jensen said the body had apparently been punctured to let the air out before sinking it, and it was weighted down in a presumed attempt to prevent it floating.
He originally claimed he had dropped her off on land on the night of August 10, according to a police statement. But police later said Madsen had provided them with a "different explanation."
The submarine was found about 15 hours after it had departed Copenhagen, on August 11. Madsen was rescued from the sinking vessel by emergency crews but there was no trace of the missing journalist. He was charged with manslaughter and ordered to be held in custody for 24 days.
His lawyer, Betina Hald Engmark, told Denmark's TV2 at the time that her client "accepts the arrest but still denies the crime."
Wall's former classmates at Columbia University Graduate School of Journalism in New York held a candlelight vigil Wednesday in her memory.
Her mother, Ingrid Wall, also posted a moving tribute to her daughter on Facebook, saying: "She gave a voice to weak, vulnerable and marginalized people. It's a voice this world needed for years to come, but that has now been silenced."
Journalist Susanne Gargiulo reported from Copenhagen and CNN's Laura Smith-Spark wrote from London.
Read More: Kim Wall case: Danish inventor to face murder charge