A policewoman almost lost an eye from injuries suffered after a homemade explosive was set off prior to the Levski versus CSKA city derby in Sofia on Wednesday.

Both the female officer and a male colleague were hit by broken glass from a window that smashed when the device exploded close to the stadium entrance, said officials from the ministry for the interior.

“It was a homemade explosive, not a rocket flare,” said the city’s assistant police chief Anton Zlatanov.

“Their injuries would have been much worse had they not been standing behind the glass door.”

According to Bulgarian media reports the female officer risked losing an eye. She underwent surgery for damage to her face.

Police interrogated dozens of fans following the match, which ended 2-2, in a bid to find the perpetrators.