An initial investigation into the bridge collapse in Pittsburgh, Pennsylvania on January 28 failed to pinpoint a cause but did find that the problem began at the bridge’s west side.

According to the Associated Press, the report noted that investigators did not discover any primary fractures in the girders they looked at that would have been considered “fracture critical,” a term defined as a beam that would likely be damaged if the bridge were to suddenly collapse.

The two-lane bridge, covered in snow, collapsed only hours before President Joe Biden’s visit to the city to speak about his infrastructure bill.

The emergency led to rescuers climbing almost 150 feet and also a human chain being formed to rescue people who were trapped in a bus stuck on the remains of the structure.

In the end, 10 people who had been in vehicles on the bridge were injured. Nearby homes also had to be evacuated as natural gas lines that had ruptured were turned off by city crews.

The National Transportation Safety Board said that it was removing components from the wreckage for closer examination. Their final report is not expected for over a year.

The bridge, which is 447-feet long, was built in the early seventies. It had shown some deterioration during a September inspection but inspectors did not consider the wear serious enough to call for it to be closed.