A total of 29 Nigerian employees of Chinese oil giant Sinopec, who were held by a local tribe in Nigeria, returned home on Friday, a Sinopec spokesperson told the Global Times Monday.

However, his statement contradicted a Reuters news report Sunday, which said that the 28 workers were kidnapped by a local criminal gang.

"Nobody was injured and the company is helping them," Lü Dapeng, the Sinopec spokesperson, told the Global Times.

According to Lü, the 29 workers lost contact with their firm after they went on a coastal exploration mission by boat along the Cross River in Akaw Ibom state on Thursday. The local branch of Sinopec immediately asked local officials and the navy to search for them.

Reuters quoted the Nigerian navy spokesman Commodore Kabir Aliyu as saying that they were kidnapped Thursday by the Lapto Marine Force and were freed in a naval operation Friday.

"We sent representatives to negotiate after learning that they were held," Lü said, adding that they were released with the help of the navy and local officials on Friday.

"The reason why they were held is still under investigation," he said. "Oil exploitation is not easy and our employees risk their lives."

"The Lapto Marine Force has been terrorizing people around Bakassi waterways, killing, robbing, as well as engaging in piracy and kidnappings," Kabir Aliyu told Reuters.

Reuters contributed to this story