The blaze, which started after an electrical short, took out three walls surrounding the centre's electrical equipment room.
So far the team has established that the servers themselves are undamaged and it looks likely that no data has been lost.
"We have just been allowed into the building to physically inspect the damage," said The Planet team in a company blog.
"Early indications are that the short was in a high-volume wire conduit. We were not allowed to activate our back-up generator plan based on instructions from the fire department."
The team is now working round the clock to fix the problem and is using parts from the company's five other data centres to re-establish the affected sites, which include popular British online forum B3ta.com.
The team had hoped to get the sites online yesterday but continuing fire service action and network issues have extended the problem.
The company has said it will reimburse customers as promised in their service-level agreements.
Fire takes down 9,000 servers
By Iain Thomson on Jun 3, 2008 7:20AM