A bridge under construction in southern Vietnam collapsed Wednesday, killing at least 18 workers and leaving dozens more missing or injured, officials said.

The bridge was being built across the Hau River, a branch of the Mekong River, in the southern city of Can Tho, a heavily traveled route that links the Mekong Delta and Ho Chi Minh City.

Thirteen bodies had been recovered at the site, and five more people died at local hospitals, said Le Viet Hung, vice chief of the Can Tho police. Nearly 100 others were injured, he said.

The exact number of missing was unknown, but on a normal day up to 140 people would work on the section of the bridge that collapsed, said Vo Thanh Tong, chairman of the Can Tho people’s committee. The collapse occurred about 8 a.m.

“We are rushing to find the missing,” Hung said. “We have mobilized emergency teams from four hospitals.”

The span was not yet open to traffic. Construction of the 1.71-mile, four-lane bridge began in 2004 and was expected to be finished next year. It was to be the largest cable-stayed bridge in Southeast Asia.

The section that collapsed was more than 98 feet tall and was above land on the bank of the river in Vinh Long Province, he said. Workers had just poured concrete on that section Tuesday, Tong said.

The bridge was being built with Japanese funding, and three companies were involved in the construction, said Furudate Seiki of the Japanese Embassy in Hanoi. He said it was still unclear whether any Japanese workers were injured in the incident.