Residents have been asked to check their gardens for "vital evidence" dumped after an attack which has left a man critical in hospital.
Police launched an attempted murder investigation after a 31-year-old man was attacked in Gershwin Road, Basingstoke, on Thursday evening.
He was later found by police in a rear garden with serious head injuries.
Det Ch Insp Justin Torgout asked people to check "gardens, sheds and bins for anything that shouldn't be there".
He said Hampshire Constabulary's major crime team was "working around the clock" to find those responsible for the "brutal" attack, and was extending "house-to-house inquiries".
Witnesses saw a group running away from the Gershwin Road area at about 23:50 GMT, he said.
They ran along the footpath between Gershwin Road and Quilter Road, towards the play area alongside Quilter Road.
He added: "It is possible that those responsible dumped vital evidence along their escape route, in the hope that it will never be found, so this is where the support of residents can prove vital.
"The response from the community so far has been great and I would like to take this opportunity to thank them for their support so far."
Police said it was a targeted attack and officers would be carrying out extra patrols in the area.
A second victim, who is 58 and from Basingstoke, was sprayed with an unknown substance and also needed hospital treatment.