WASHINGTON, Jan. 19 (UPI) -- Sagging on an interstate highway bridge in Ohio in 1996 was caused by problems like those investigators found on the collapsed I-35W bridge in Minneapolis.

Preliminary findings released this week by the National Transportation Safety Board said 16 of the Minneapolis bridge's gusset plates fractured. The plates connect beams on the bridge.

While a Federal Highway Administration report that was also released at an NTSB news conference mentioned the I-90 bridge in Ohio, agency officials suggested the problems with the Minneapolis bridge had never been seen before, The St. Paul Pioneer Press reported.

The NTSB did not investigate the Ohio bridge closing. An Ohio Department of Transportation report blamed the sagging on beams that "were not adequate to support the design loads of the structure."

While the NTSB is known for its investigations of plane crashes, it has little experience with structural failures, the newspaper said.

Thirteen people were killed and scores injured when the I-35W bridge collapsed suddenly at rush hour Aug. 1, 2007. The sagging of the bridge over the Grand River in Ohio caused no injuries but the closing caused massive inconvenience.