South Africa ? Singing and dancing despite exhaustion, the last of 3,200 miners trapped deep underground for more than a day emerged safely Thursday night, delivering a happy ending but raising questions about the safety of South Africa’s important gold mines.

Government officials announced that the Elandsrand mine, one of the top producers in the world’s leading gold-mining nation, would stay shut for at least six weeks while experts studied what caused a pipe to break and crash down the main shaft Wednesday, knocking out the elevator.

The national miners union threatened unspecified “industrial action” against the mining business, accusing managers of earning fortunes while compromising on safety. It said that among other things, companies have let alternative escape routes flood rather than maintain them.

The final group of 45 workers brought out through an auxiliary shaft normally used to remove debris arrived at the surface shortly before 9 p.m., walking out caked in dust but otherwise healthy a day and a half after the accident.