Assistant Chief Constable Steve Cotterill said "please do not see these two arrests as the police inquiry coming to an end" and appealed to the public for additional information.
He said: "I need additional information from the public out there to really get to the truth to what was the reason behind that fire - whilst I know the cause I do not know the reason behind it and I'm still anxious for that information to come forward."
More top news
Leicester City's victorious players spotted a man who looks uncannily like star striker Jamie Vardy and invited him on to their bus.
Weather finally looking up this week.
If Donald Trump wins here tonight, it is a near-fatal blow to his rivals. Ted Cruz and John Kasich will be under pressure to drop out.