People, including members of South Central Ambulance, have left floral tributes to those affected by the incident at nearby Bicester Fire Station.
Jamie Jessett, from the town, said he went to school with one of the firefighters who died, but declined to name them to the BBC.
He said the fire was "devastating", but also that it was "amazing" to see the community come together to pay their respects.
"That's what we need, especially at this moment in time," he added.
Calum Miller, MP for Bicester and Woodstock, travelled from London to the site, where he told the BBC: "I understand from the fire service that firstly they are making sure everything is secure, and then of course in the fullness of time there will be an investigation."
He added he was "devastated" and said his thoughts were with the families and friends of those who had died, and with the two firefighters in hospital.
"It's a terrible thing to have happened, and I know it's a tight-knit community who are already showing their support for those families," he said.
The MP said he was "in awe of the bravery of those who put themselves in the front line whenever there is danger".
"It's an incredible commitment, it's an incredible path of service, and it's just so tragic that two members of that community have lost their lives," he said.
Leader of Oxford City Council, Councillor Susan Brown described it as a "terrible reminder for us all that firefighters, as well as the other members of the emergency services, put themselves at risk on a daily basis, to protect us all. We owe them a deep debt of gratitude".
Oxford City Council has lowered the city flag, flying over Oxford Town Hall, to half-mast in tribute.
St Laurence's Church in Banbury Road, Caversfield, close to the site, said it had opened its doors "for anyone looking for a space for private prayer or for stillness and reflection" following the "tragic news".
A book of condolence has also been opened at the church, as well as at Garth House – Bicester Town Council's headquarters.
