Sources from the National Transportation Safety Board said the investigations on the Minnesota bridge collapse that killed 13 people and injured 100 on August 1st came to the conclusion that the design of the bridge had flaws, which is not a singular case among the bridges across the United States. The Interstate 35W Bridge across the Mississippi river was designed 40 years ago, but the multiple modifications that were made afterwards apparently did not take into consideration the consequences they would have on the base structure of the bridge.

The board of investigators is expected to make an official statement later on Tuesday at a news conference regarding the causes of the collapse and whether this situation in particular applies to other bridges across the nation too. The departments for transportation safety are planning for a new series of inspections, which usually include corrosion and age-related problems.

The unexpected incident that took place over six months ago during rush hour and right in the middle of another renovation project, was what experts call a “fracture critical”, which means any of the plates could have been responsible for the collapse. Board officials anonymously unveiled that although the extra pressure from the equipments and materials could have affected the plates, there was no exact conclusion on whether they were the cause for the collapse.

However, in order to prevent that from happening again, NTSB representatives are expected to implement a few changes in the additional construction procedures, as investigations on how the extra weight might affect the bridge have not been conducted in this particular case. This measure would be especially needed considering the age of some bridges and the risks of another collapse.

In the meantime, the highway departments do not seem to appreciate this particular design for bridges, which has been highly popular 40 or 50 years ago. There are still 465 bridges with a similar type of construction, but engineers these days design the bridges so that in case a girder or plate breaks, it will not cause the whole structure to collapse.