Officials in Heilongjiang Province on Friday explained that the fatal bridge collapse that killed three and injured five in the provincial capital Harbin was due to vehicle overload.

A ramp, about 3.5 kilometers from the main structure of the Yangmingtan Bridge, tilted to one side and crashed onto the ground at 5:30 am, said Sun Qingde, deputy head of the construction committee of Harbin, the Xinhua News Agency reported.

Four full-loaded heavy trucks were driving along the near-side lane and plummeted 30 meters to the ground, officials announced Friday.

Two people were killed on the spot and six more were injured, with one dying later in hospital. 

"I was dozing off in the truck when suddenly it rolled over and fell to the ground. It was terrifying," Liu Guodong, one of the survivors, told Xinhua.

Traffic on the bridge has now resumed, except for the collapsed section, a local publicity official told the Global Times.

Responding to questions at a news conference in Beijing on Friday, Huang Yi, a spokesperson of the State Administration of Work Safety, said the bridge must have had some fault since it had been built less than a year before the collapse.

He vowed that the results of a probe into the disaster would be divulged to the public immediately upon completion.

Huang Yusheng, a deputy secretary-general of the city government of Harbin, told reporters that, based on an initial investigation, the cause was attributed to overloaded trucks but that a formal conclusion would not be drawn until the team finished the probe.

"This has nothing to do with the previous pavement collapse incidents in Harbin and we will conduct a full check on all roads and bridges in the city," Huang Yusheng said.

Earlier this month, Harbin was rocked with a series of seven pavement collapses, causing two deaths and two injuries. 

Yangmingtan Bridge was opened to traffic in November 2011 and its construction cost 1.88 billion yuan ($296 million).

With a total length of more than 15 kilometers, spanning the Songhua River in Harbin, the eight-lane bridge was claimed to be the longest in northern China.

Construction only took 17 months, which was reported by the Heilongjiang Television as being a miraculous achievement for Harbin at the time.

Some witnesses posted photos online and pressed the local authorities to find out how the bridge had collapsed so soon.

Li Faxiong, a professor with the civil engineering department at Tsinghua University, told the Global Times that an overload of vehicles might have been a contributing factor but that the bridge's structural integrity should be thoroughly checked. 

Tan Danhui, an associate professor at the Center for Bridge Safety Tests at Tongji University, said that traffic volume is an essential element that should have been thoroughly taken into consideration during the design and construction of the bridge.

There have been at least six major bridge collapses across the country since July 2011 with shoddy construction and overloading being blamed, Xinhua reported.