SAO PAULO, Brazil - Brazilian prosecutors are threatening to halt construction at the already delayed stadium hosting the World Cup opener in Sao Paulo because of concerns related to workers' safety.

Prosecutors said Thursday they found irregularities at the Itaquerao Stadium where nearly 20,000 temporary seats are being installed for the high-profile opener between Brazil and Croatia in four weeks.

They said constructors had already been advised about the safety problems a few weeks ago, but nothing had been done by the time inspectors returned to the Itaquerao on Thursday.

The company in charge of the temporary seats dismissed the possibility that work would be stopped. It said the prosecutors' complaints were about minor issues and all of the alleged problems would be resolved by the end of the day.