Rescuers on Wednesday continued searching for 3 Filipinos and 3 Indonesians feared trapped under mounds of rubble after a bridge in Taiwan collapsed onto several fishing boats moored underneath, an official said Wednesday.

CCTV footage captured the moment the 140-meter long single-arch bridge tumbled down onto at least 3 fishing boats as a petrol tanker that was crossing also plunged into the water in Nanfangao, on Taiwan's east coast, early Tuesday.

Relatives confirmed that 2 of the 3 missing Filipinos were inside one of the fishing boats pinned by the bridge. Three Indonesians also remained missing, said Manila Economic and Cultural Office (MECO) Director for Administration Gerry De Belen.

"Nagsasagawa pa rin ng retrieval operation. Nahihirapan silang iahon iyong kalahati ng fishing vessel na nasa ilalim ng tubig. Iyon ang napuruhan ng structure," he told radio DZMM.

(Authorities are still conducting retrieval operation. They are finding it difficult to lift half of the fishing vessel that is still submerged. That part was hit worst by the structure.)

The accident, he said, wounded 5 other Filipinos, 4 of whom were discharged from the hospital while one remained under observation.

HOPES FADING

Yilan Fire Department chief Hsu Song-yi said rescuers were having difficulty accessing the 2 remaining vessels which were underwater in low visibility.

"This is a complicated rescue operation. We were in consultation with structural and building experts as well as ship-building experts, and therefore it has taken us longer. We are doing our best," he said.

A local official who spoke on condition of anonymity said that even if the workers survived the impact of the collapse, "the air might not last this long."

It is not immediately clear what caused the bridge -- which was completed in 1998 and spanned a small fishing port -- to collapse.

Taiwan was skirted by a typhoon on Monday night, which brought heavy rains and strong winds to parts of the east coast.

But at the time of the bridge collapse, the weather was fine.

The 20-year-old bridge previously survived several earthquakes, noted MECO's De Belen.

TAIWAN'S QUAKES, FISHING INDUSTRY

Taiwan lies near the junction of 2 tectonic plates. The island's worst tremor in recent decades was a 7.6-magnitude quake in 1999 that killed around 2,400 people and destroyed tens of thousands of buildings.

Although the devastating quake had ushered in stricter safety codes, several fatal incidents in recent years have triggered probes into shoddy construction.

In 2018, a developer, an architect and a civil engineer were indicted over the partial collapse of a building that killed 14 people during an earthquake earlier that year.

It followed a similar incident in 2016 when another quake killed 117 people -- most in a single apartment block that collapsed.

Taiwan also has a huge fishing industry and many of those who work on its boats are low-paid migrant workers from countries such as the Philippines, Indonesia and Vietnam.

Prosecutors have launched an investigation into the cause of the incident, said transport minister Lin Chia-lung, adding that the bridge was still within its expected 50-year lifespan.

"Recent weather conditions, earthquakes and past assessments of the bridge will be taken into considerations. We will fully cooperate with the investigation," he told reporters.

Previous serious bridge incidents in Taiwan have mostly been related to typhoons.

In 2009, 2 bridges were badly damaged by Typhoon Morakot, which left more than 400 people dead.

— With a report from Agence France-Presse