In all, 16 people were injured when the roof at the southern end of the FC Twentestadium collapsed around midday on Thursday (local time), said Peter den Oudsten, mayor of the Dutch town of Enschede where the football stadium is located. Three people were treated at the scene, he said.
Den Oudsten said two injured workers had gone to hospital on their own for treatment before returning home. He added later Thursday that one of the hospitalized victims remained in "a very critical condition" in hospital.
FC Twente chairman Joop Munsterman said the entire club was in shock.
"You see this kind of thing in a disaster movie, but not in real life," he said.
News video showed at least one construction worker, apparently bleeding from a head wound, being taken away by paramedics.
Sniffer dogs and cameras were used to search for anybody else still trapped under the tangle of girders and red roof panels - the colour of FC Twente's shirts - behind the goal at the southern end of the Grolsch Veste stadium. By the end of the afternoon, the search was halted and Den Oudsten said emergency services were sure nobody else was trapped.
The cause of the collapse was under investigation by workplace inspectors and prosecutors. The construction work aimed to increase the stadium's capacity to 30,000 from 24,000 by adding a new tier above existing seating.
FC Twente director Jan van Halst said the club "is terribly upset. Our sympathy goes to the victims."
The FC Twente team, which was the Dutch national football champion in 2010 and runner-up last season, was training in the southern province of Zeeland at the time of the collapse.
Twente is in the third qualifying round of next season's Champions League and scheduled to host a match in Europe's most prestigious club tournament on July 26-27 or Aug. 2-3. The exact date will be decided by UEFA, the European football body, next week.
Munsterman said he "had no inclination at all at the moment to even think about" where the Champions League match might be played.
A friendly preseason match between Twente and a team from Zeeland was cancelled.
The stadium is on the edge of Enschede, 160km east of Amsterdam.
