Detectives investigating the "brutal" killing of a man stabbed to death on a Cambridge common have made two arrests.
Peter Mark Anderson, 46, of Heath House in Cambridge, was found near Stourbridge Common in the city on 25 July. He died later in hospital.
A 17-year-old boy from London was arrested in Cambridge on suspicion of murder, police said.
A 33-year-old Cambridge man was also arrested on suspicion of assisting an offender and supplying of drugs.
They both remain in custody at Parkside Police Station.
A 36-year-old man arrested on Saturday on suspicion of murder was released pending further investigations.
Officers have spent the day at the common, marking one week since Mr Anderson's death by handing out leaflets and appealing for witnesses.
Detectives are asking in particular for a group of teenagers who first raised the alarm to come forward.
Det Ch Insp Mike Branston, leading the investigation for Cambridgeshire Police, said officers would be on the common looking for witnesses who may have been there at the time of the incident - about 16:15 BST - a week ago.
As well as the group of teenagers, he said officers were keen to talk to a young man who was seen cycling past at the time of the attack.
"[We] believe people with potentially crucial information have still not come forward," the detective added.