Schalk Van Zuydam, Associated Press
Two gold miners who had been trapped a mile underground smile Thursday as they are greeted near mine entrance.

JOHANNESBURG, South Africa — One day after a freak accident stranded 3,200 gold miners more than a mile underground, South African officials said Thursday that they had closed the huge Elandsrand mine for up to six weeks to determine the cause of the mishap.

The mine's owner, Harmony Gold, had lifted all of the miners to safety by about 9 p.m. Thursday, the Associated Press reported, using an undamaged auxiliary elevator in a ventilation shaft. One miner fell while awaiting rescue and was carried out on a stretcher, but no one else had been injured, a Harmony spokeswoman, Amelia Soares, said in an interview.

Rescuers had said that they would free the remaining miners by midday, but that deadline passed with hundreds still underground, and it appeared unlikely that the last workers would reach the surface until late Thursday.

The thousands of miners, including hundreds of women, were trapped more than a mile underground about 10 a.m. local time Wednesday when a 50-foot section of compressed-air pipe and its concrete base broke loose and fell down the mine's main shaft. The pipe severely damaged the shaft's steel frame and cut power cables to the main working area.

Harmony did not announce the accident until Wednesday evening, about 10 hours after it occurred, a second spokeswoman, Lizelle du Toit, said in an interview. She said the company had held back word of the accident because it originally believed that the workers would be quickly brought out.

The Elandsrand mine, about 40 miles southwest of Johannesburg, is like many aging mines on South Africa's Witwatersrand, the biggest and most heavily mined gold deposit on Earth. Gold production had dwindled sharply when Harmony bought it in 2001 and began digging a new mine beneath the old one. Harmony has said that it is investing about $90 million in mine improvements to tap the nearly 7 million ounces of gold that are known to exist.

South Africa's minerals and energy department closed the mine after the National Union of Metalworkers of South Africa, the miners' labor union, charged that the accident was the result of poor safety standards and Harmony's practice of operating the mine around the clock. "We suspect negligence," the union president, Senzeni Zokwana, told reporters on Thursday.

Harmony officials rejected both charges, and said that the mine shaft had passed a required weekly safety inspection on Saturday. But the company's chairman, Patrice Motsepe, said that the accident underscored the need for more stringent mine-safety efforts, saying that "our safety records both as a company and as a country leave much to be desired."

The government has set a goal of reducing mine deaths by 20 percent annually. But roughly 200 of South Africa 400,000 mine workers died in both 2005 and 2006, and the pace this year so far is about the same.