There was no official confirmation from the team or their Austrian owners.
"It's been done, there's a complete state of shock in the organisation," the source said on condition of anonymity.
Purnell was the principal who oversaw the transition from Jaguar to Red Bull when Austrian billionaire Dietrich Mateschitz bought the team from Ford in November. Pitchforth was managing director.
The Autosport website reported that Christian Horner, British boss of the championship-winning Arden F3000 team, was lined up to take over as head of the team.
Briton David Coulthard is due to race for the team this season. The second driver has yet to be decided, with Austrian Christian Klien and Italian Vitantonio Liuzzi rivals for the seat.
Liuzzi won last year's F3000 title with Horner.
