Forensic officers searched a caravan site four kilometres from where a policeman was killed while following up on a reported burglary.
Andrew Harper died after attending the scene in Berkshire, west of London, at around 11.30 pm local time (00.30 CEST) on Thursday, say Thames Valley Police.
Thames Valley police have launched a murder investigation and have arrested ten people on suspicion of murder. They and are currently in police custody at various police stations across the Thames Valley. The youngest is 13, while the oldest is 30.
Forensic officers searched a caravan site on Saturday where two vans were reportedly blocking the entrance.
Police did not comment on whether any of the suspects lived at the caravan site but said: "This police presence forms part of the investigation following the death of PC Andrew Harper. Officers are at the scene making inquiries.”
Jason Hogg, the force’s deputy chief constable, said: “Our deepest thoughts at this time are of course with Andrew’s friends and family, who are being supported by specially trained family liaison officers.
“Our thoughts also extend to all of Andrew’s colleagues within Thames Valley Police.
“As a force, we are devastated at the loss of our colleague and will all be supporting each other at this difficult time.”
The incident happened at Sulhamstead, near Reading.
Boris Johnson, UK prime minister, said: "I am deeply shocked and appalled by the death of a brave officer on duty in Thames Valley last night.
"My thoughts are with PC Harper’s family, friends and colleagues at this terrible time.
"It is the most powerful reminder that police officers up and down the country put themselves at risk every single day to keep us safe.
"They have my absolute support."
The Thames Valley Police Federation has also released a statement.
"Death of our colleague PC Andrew Harper has been confirmed by Thames Valley Police.
"This is totally devastating news. All our thoughts - and the thoughts of the entire police family across the UK - are with the family, friends and close colleagues of PC Harper who died last night.
"Police officers go to work each and every day to do their duty. We are courageous, caring and compassionate. We confront danger on a daily basis. We know there is a risk when we put on the uniform but we do so as we are proud to protect the public.
"Sadly on very rare and horrendous occasions, a colleague makes the ultimate sacrifice. We will ensure that heroism is never forgotten.
"We are offering our full support to the officer’s family and colleagues at this simply awful time."