The mill area is a complex that is dozens of meters tall. The actual mill is located at the lowest level.
There are four cement mills at the factory, with the third one being the smallest and located in the corner. Next to it are three bigger ones, situated 10 m above the ground.
The third mill, which was involved in the deadly accident on Monday, is located about a meter away from the ground, spanning 7 m in length.
A team of three performed reparations outside of the mill on Monday, cooperating with seven others inside the mill.
Nong Van Tuan, 29, and two other people who performed maintenance outside the mill fell off when it started rotating. They are being treated at Yen Bai general hospital and all are stable.
The seven people who were inside the mill at the time died.
According to a report by the Yen Bai labor confederation, the seven deceased workers are Nong Van Toan, 33; Nong Van Thuat, 39; Mai Thien Hoang, 37; Le Manh Cuong, 45; Pham Xuan Truong, 47; Pham Ngoc Linh, 33; and Nguyen Doanh Manh, 42.
Thousands of marbles fell to the ground near the entrance of the mill as it rotated.
Tuan said: "Replacing the eroded plates is a routine done every 5-7 months. Things usually go well, but there was an incident this time."
He said the mill started to operate again around 35 minutes after the workers went in. The three workers stationed on the roof of the mill fell to the ground.
Tuan knew his coworkers were still inside the mill, so he tried to hop with one leg towards the control room to cut off the power source.
"Everything happened too fast. There was no-one at the control room at the time," he said, adding that he had no idea how the machines operated by themselves.
Yen Bai authorities said the incident had to do with issues with the mill's motor engine.
Ha Tat Thang (C), head of the Department of Work Safety under the Ministry of Labor, Invalids and Social Affairs, speaks with workers at the scene. He has requested relevant parties to form inspection teams to ensure work safety.
Thang also requested the firm involved to find the cause of the incident to prevent future mishaps.
On Monday night, Prime Minister Pham Minh Chinh instructed authorities to figure out the cause of the accident, support victims' families and evaluate the cement processing procedures to resolve issues.
Yen Bai Cement and Minerals began as a state company formed in 1980. In 2004, it began to operate as a joint stock company with a charter capital at VND118 billion ($4.63 million), dealing in limestone and cement, as well as minerals, real estate and transport.
The scene of the incident which caused the death of seven workers. Video by VnExpress/Anh Phu
