Part of the roof of the FC Twente football stadium in the eastern Netherlands collapsed on Thursday during building alterations, killing one person and injuring 14 others, a city official said.
"It is terrible. One person has died and 14 others were injured. Ten of them were taken to hospital. Two of those are seriously injured," Mayor Peter den Oudsten told a press conference in the city of Enschede.
"We cannot at this stage give the figure with absolute surety," he added, saying "we have to make sure that nobody else remains trapped under the rubble."
The incident happened around noon when construction workers were working near the roof of De Grolsch Veste stadium in Enschede, 163 kilometres (101 miles) east of Amsterdam.
Den Oudsten did not want to speculate on the cause of the accident, saying it would be investigated. Neither could he give details on the person who was killed, believed to be a construction worker.
"The moment we know what had caused it, we will make it known," Mayor Den Oudsten promised.
FC Twente manager Jan van Halst urged fans not to go near the stadium until the area had been cleared.
"Our condolences go out to the family of the deceased and those who were injured," he added.
Van Halst confirmed that construction work was happening at the club when the incident happened.
Television pictures showed the part of the club's red roof having collapsed on to an embankment on one of the goal-ends of the stadium, trapping people underneath. Paramedics could be seen removing the injured from the scene.
Witnesses told how they saw construction workers running away from the work site at stadium as it started to collapse, ANP news agency reported.
"It collapsed with a huge noise like a house of cards," a witness, who saw the incident from an office next to the stadium, told the agency.
"I heard a huge bang and there was big noise," another witness told local television.
FC Twente plays in the Dutch first division, and were league champions last year.