Armed police officers are scouring Didcot, Oxfordshire, and its surrounding areas, after the bodies of Philip Howard, 44, Janet Jordon, 48, and daughter Derin were discovered in a house in Vicarage Road just after 8.20pm on Saturday, following a call from a member of the public.
More than 100 officers are also searching Oxford University Parks where Allen worked as a groundsman.
Police also revealed they have found what they believe is the murder weapon at the crime scene.
Detective Superintendent Chris Ward, the head of Thames Valley Police's major crime unit, said they believe Jed arrived in Oxford by train from Didcot at 5.45pm on Saturday.
Det Supt Ward said: "Jed is wearing a red or maroon shirt, a dark hooded jacket with a white trim on the zip, blue jeans and black shoes.
"After visiting WH Smith, we believe that Jed then walked to Oxford University Parks."
An alphabetical guide to your new and returning MPs in the Thames Valley.
For a look at the seats which will be most fiercely fought in the Thames Valley - Rachel Hepworth.
Now, some young people say they're just not interested in politics. But with the General Election fast approaching on May the 7th, all the political parties are trying their best to change that. And to win the young vote.
So to find out what they had to offer them, in their area, sixth formers at a school in Wantage organised their own Hustings. Andrew Pate has more.
The Thames Valley will be a key battleground in the General Election for all the major political parties.
ITV Meridian's Fred Dinenage speaks to Professor Colin Rallings, ITV's political expert, about which seats are crucial to the formation of the next Government.
Rail passengers are being warned to check before travelling over Easter because of disruption on routes between the Thames Valley & London.Read the full story ›
A former police detective says child exploitation in the Thames Valley could have been prevented years before a widespread investigation got underway. Dermot Norridge says he repeatedly raised concerns over the plight of a 13-year-old girl, but was ignored by senior care bosses. Well today, he's been speaking to our reporter Cary Johnston, about his frustration.
Yakubu came off the bench to score his first goal for Reading and secure an FA Cup fifth round victory at Derby.
Hal Robson-Kanu gave the visitors a 53rd-minute lead after Stephen Warnock had been sent off on his Derby debut.
It took Darren Bent eight minutes to level the scores - with his fifth goal in as many games.
Yakubu - who was only signed last month - held off the chasing defenders to fire in a low-left footed shot.
Severe delays on M40 northbound - closed between junction 9 A34/A41 (Wendlebury/Bicester) and junction 10 A43 (Brackley/Cherwell Valley Services). It's due to a serious accident involving 42 vehicles. It happened at 07:50 this morning, just after junction 9. The carriageway is expected to be closed for the rest of the day. Trapped traffic is being turned back to J9. There are solid queues of several miles approaching the closure.
Diversion - the official diversion is along the southbound A34 to Weston-on-the-Green, then the B430 northbound, rejoining at J11. This route is signed by the solid circle symbol