Stewards investigated the opening lap incident, which happened at the kink on the Kemmel Straight, but decided no action was necessary.
Video footage shows that Razia was drawing alongside second-placed Calado, but was not completely level with him.
Calado took his usual racing line, which forced Razia onto the grass and caused him to spin across the track in front of the majority of the pack at 150mph.
The only car Razia took out as he spun was Davide Valsecchi, ironically the man he is tied on points with in the championship.
"I had a good start and felt sure I could take second place on the run to Les Combes," said Razia.
"I thought I was aiming for a legitimate gap, but Calado came across and I ended up on the grass.
"I had a speed advantage coming out of Raidillon onto the straight, but in my opinion some drivers don't use their mirrors."
Interviewed directly after the race on the podium, Calado said: "I don't know what happened on the first lap, I need to have a look at it."
Calado gained 10 points on Razia and Valsecchi with his second placed finish at Spa, and is 44 points behind with four races remaining.
- Davide Valsecchi