Dozens of construction workers died and many were seriously injured when a section of a bridge in south Vietnam collapsed Wednesday, officials said.

Authorities in the Vinh Long province said at least 38 workers died and dozens were trapped under piles of rubble when a 74-metre-long section of the Can Tho bridge collapsed early Wednesday.

Approximately 200 persons were working on the 2.7-kilometre bridge built over the Hau River when the section collapsed for unknown reasons. Rescue teams scrambled to find survivors and authorities quickly brought three large cranes to assist the operations.

Large pieces of concrete and twisted steel buried dozens of people, authorities saying several had the strength to call for help and communicate with rescue workers.

Many were killed on the spot, while other died of their injuries at the hospital, raising the death toll to 38, a police official said.

Media said nearly 100 persons were rescued from the huge piles of concrete and steel and transported to nearby hospitals with improvised stretchers and vehicles arrived at the site.

The concrete blocks collapsed over the river’s banks after a loud noise was heard, as one of the men supervising the operations said.

The worker told a local newspaper that a terrifying sound shattered the calm and immediately after that the whole section crumbled. He described “a horrible scene” with concrete blocks falling on people working below, as clouds of dust covered the sky.

Soldiers and students across the country were asked to donate blood for the victims of what is said to be the largest construction accident in years.

The Can Tho cable bridge was supposed to be the longest in South-East Asia and the 343 million dollars needed for its construction were provided by Japan. The construction began in 2004 and was due to be completed next year.

It would offer people the possibility of crossing the Hau River faster, without being forced to use the ferry between Can Tho and Vinh Long provinces.

An investigations has been launched to determine the accident’s cause, preliminary assessments saying the scaffolding might have been removed to early or couldn’t support the massive structure.