A second blaze was also extinguished at the same time. Tests were being carried out to assess the damage which may have warped the structure.
John Anderson,a Fire Station Officer at Foleshill told the CET: "They have been quite fortunate. If it had occurred in the middle of the night it probably would have been much more developed.
"The fire was about 10 metres by 10 metres but it looked more impressive than it actually was.
"The seats are basically made from petrol and that's why they burn so badly.
"The site managers are worried that the steel structure may have to be removed and also the concrete. If it has to come out it will cause some problems."
Arena Chief Executive Paul Fletcher not surprisingly played down the incident say: "“I believe that there is absolutely no major structural damage to the Arena. One or two seats and packaging materials were set on fire but the seats can be replaced quite easily.
“There is security on site, which is the responsibility of the builders – Laing O’Rourke. It is a huge area to cover at that time of night, but obviously we will sit down with them to see if there is any more that can be done.
“It won’t make any difference to the schedule of the Arena. It is still scheduled to be ready for the start of the new football season.”