Brazilian officials found 163 Chinese nationals working in "slavery-like conditions" at a construction site for a factory owned by Chinese electric vehicle producer BYD in Brazil's Bahia state, the local labor prosecutor's office said during a news conference on Monday.

According to the authorities, the workers were hired in China by another firm and brought to Brazil irregularly. They were laboring for long hours, in excess of what is allowed by Brazilian law, sometimes for seven days a week straight, while being kept in what authorities described as degrading conditions in their accommodations, among other labor violations.

BYD did not immediately reply to a request for comment. The labor authorities did not disclose the names of the firms involved in hiring the workers.

In Brazil, "slavery-like conditions" include forced labor, but also covers debt bondage, degrading work conditions, long hours that pose a risk to workers' health and any work that violates human dignity.

The workers had to request permission to leave their lodgings, and at least 107 also had their passports withheld by their employer, said labor inspector Liane Durao, adding that conditions at the work site were dangerous.

"We found that the work of ... these 163 workers, was carried out in slavery-like conditions," she said.

"Minimum safety conditions were not being met in the work environment," said Durao.

The operation is ongoing, said Durao, and fines have not yet been issued.