"We don't who [they] are yet but we will when we get to court this morning," Anderson said.
Blackmoore was 21 years old and 10 weeks' pregnant when she died after being viciously assaulted at her home in Wainoni on August 17, 1995. Her 2-year-old son was sleeping in his bedroom at the time of her death.
Anderson said Blackmoore's son Dillon, who was now 26, was the first person he called after being contacted by police.
Detective Sergeant Todd Hamilton said the investigation into Blackmoore's death remained ongoing and detectives were committed to ensuring all those involved were held to account.
"Our thoughts are with Angela's family at they continue to mourn her tragic death.
"Police would like to thank members of the public for information provided following a renewed appeal in May 2019.
"As the matter is now before the court, police is unable to provide further comment," Hamilton said.