Rotterdam’s mayor Ahmed Aboutaleb has said banishing flares from football matches is an almost impossible task because fans smuggled the explosives into the stadium in “intimate parts” of their body.

The Dutch cup final on Sunday was twice suspended after fans of the two clubs, Feyenoord and NEC Nijmegen, set off fireworks and flares in Rotterdam’s De Kuip stadium.

Referee Serdar Gözübüyük called the players off the pitch after 13 minutes after thick clouds of smoke billowed across the pitch from the stands, while in the second half the players spent 20 minutes in the dressing room after a banner was set on fire behind one of the goals.

Aboutaleb pleaded with fans to stop bringing flares to matches, but admitted that there was little in practice that he could do to stop them.

“I was told that the toilets behind the stands were full of condoms that they stuffed the flares in so they could hide them in intimate places,” the mayor said, adding that both men and women used the technique.

Cavity searches at football matches would be inappropriate and violate fans’ privacy, Aboutaleb said, while “Chinese” methods such as using X-ray devices “go too far for me”.

The football association KNVB said it would not comment on “speculation about how fireworks were able to get into the stadium”, but admitted it was limited by privacy rules.

“We’re not allowed to frisk intimate areas,” a spokesman said. “It seems supporters are inventive and have found all kinds of ways in the past to smuggle fireworks into stadiums”.

Feyenoord won the match 1-0 to claim the Dutch cup for the 14th time, while NEC Nijmegen’s wait for a first win goes on after they took the runner’s-up medals for the fifth time.