Video footage from a transit bus of the Fern Hollow Bridge collapse this year shows one end of the structure had already fallen when an expansion joint at the other end was pulling apart, federal investigators said Thursday.

The National Transportation Safety Board issued an update on the Fern Hollow bridge collapse, saying the video is giving them more information about the sequence of events.

So far there’s no evidence of “widespread deficiencies” in the “rigid K-frame superstructure types” that form the bridge’s basic structure, the report said.

The investigative update said that all aspects of the disaster are still being looked at and that the cause has yet to be determined. Investigators plan mechanical and chemical testing on material samples and will examine plate dimensions and weld quality.