JAKARTA - Rescuers hunted for survivors on Sunday after a busy bridge spanning the Mahakam river in Indonesia's Borneo island collapsed, killing four people and injuring 19 others, officials said.
President Susilo Bambang Yudhoyono has ordered an investigation into the accident, which saw hundreds of vehicles thrown off the 720-meter-long (yard) structure -- built to resemble San Francisco's Golden Gate Bridge.
Witnesses reportedly heard a loud crashing sound as the bridge buckled, sending a public bus, cars and motorcycles plunging into the broad river in Kutai Kartanegara district.
Survivors desperately swam to the shore, screaming in panic, while others were trapped underwater beneath the debris.
"We have recovered four bodies and rescued 39 people," East Kalimantan province's search and rescue agency head Harmoni Adi told AFP.
"Rescuers are diving in the river to search for survivors but it's difficult because of low visibility under water and strong currents. I don't know if we can find more survivors but the search will continue," he added.
The cause of the collapse was not immediately clear, but disaster management agency spokesman Sutopo Purwo Nugroho said a steel support cable snapped as workers were repairing it.
"That probably caused the collapse," he told AFP.
"We don't know how many people exactly were missing. Several of them were workers," he said.
The incident left another 19 people injured, 10 of them seriously, said Nugroho, adding that they are in a stable condition.
Witnesses told tales of miracle survival after being flung from the bridge.
One survivor, 40-year-old Adam Nur, told Kompas.com news website he had swum 300 meters to shore after disaster struck when he and four friends were driving over the structure.
"I was texting when suddenly something hit my shoulder and I couldn't move my left hand. Water was quickly filling up the car so I broke a glass window, got out and luckily for me, I knew how to swim," he said,
"My will to live gave me the strength to swim, using only an arm. I heard that my four friends were all safe," he added.
Three ministers including Welfare Minister Agung Laksono arrived at the site early Sunday to oversee rescue operations and investigate the cause of collapse, ministry spokesman Tito Setiawan told AFP.
"The president has instructed them to find out why the bridge collapsed and what follow-up actions were needed such as provision of aid to the victims and their families," he said.
Setiawan said the government will now operate ferries to transport people across the river.
Authorities said the bridge was built in 2002 over the Mahakam river -- the longest in East Kalimantan -- and linked the towns of Tenggarong and Tenggarong Seberang in the province.
Indonesia is a member of the Group of 20 bloc of major economies, and is setting a blistering growth pace expected to top six percent this year.
But investors complain its infrastructure is hopelessly inadequate for the pace of growth it hopes to sustain in coming years, and it is also mired in corruption and red tape.
The government last year announced plans to spend 140 billion dollars on infrastructure until 2014, more than half of which would have to come from the private sector.
In 2009, Indonesia opened the 5.4-kilometer (3.3 mile) Suramadu bridge linking second biggest city Surabaya to less-developed Madura island.
The bridge, the country's longest, was built with the help of a loan from China.