Investigators on Thursday were examining possible structural problems surrounding a bridge that collapsed in northeastern Taiwan, killing six people.

A 2016 report on bridges in Yilan county had found problems with the expansion joints on the Nanfangao bridge, which was completed in 1998 and collapsed on Tuesday morning, the official Central News Agency reported. The joints are designed to absorb changes in temperature.

CNA said the report had said that motorists could sense a difference of levels on either side of the joints, possibly as a result of warping or other problems.

The company responsible for managing the bridge, Taiwan International Ports Corporation, earlier said it had cleaned the joints and fixed other problems such as rusted steel reinforcements and crash barriers in 2017 and 2018.

Investigators are also looking into the condition of the bridge’s steel cables, including the possibility of dangerous levels of corrosion.

The bridge, which is 140 metres (460ft) long and 18 metres high, collapsed into a bay on Taiwan’s lightly populated east coast, about 60km (40 miles) southeast of Taipei.