The temperature outside the factory yard was more than 100 degrees on a September visit. Several feet from where the metal was being poured, the area felt like an oven, and the workers were slick with sweat.

Often, sparks flew from pots of the molten metal. In one instance they ignited a worker’s lungi, a skirtlike cloth wrap that is common men’s wear in India. He quickly, reflexively, doused the flames by rubbing the burning part of the cloth against the rest of it with his hand, then continued to cart the metal to a nearby mold.

Once the metal solidified and cooled, workers removed the manhole cover casting from the mold and then, in the last step in the production process, ground and polished the rough edges. Finally, the men stacked the covers and bolted them together for shipping.

Image As metal pours into ladles, sparks fly, sometimes igniting workers clothing, at Shakti Industries in Haora. Plant officials say accidents do not occur. Credit... J. Adam Huggins for The New York Times

“We can’t maintain the luxury of Europe and the United States, with all the boots and all that,” said Sunil Modi, director of Shakti Industries. He said, however, that the foundry never had accidents. He was concerned about the attention, afraid that contracts would be pulled and jobs lost.

New York City’s Department of Environmental Protection gets most of its sewer manhole covers from India. When asked in an e-mail message about the department’s source of covers, Mark Daly, director of communications for the Department of Citywide Administrative Services, said that state law requires the city to buy the lowest-priced products available that fit its specifications.

Mr. Daly said the law forbids the city from excluding companies based on where a product is manufactured.