GREEN BAY, Wis. -

Transportation officials said the cause of a dip in the Leo Frigo Bridge last month was due to support poles beneath the pier buckling.

The state Department of Transportation Northeast Region in Green Bay said  Thursday that the bridge deck and Pier 22 of the Leo Frigo Bridge "appear to be in good shape," but pilings for the pier were warped due to corrosion. Experts investigating the 2-foot dip said the corrosion was caused by soil composition and the rise and fall of the water table.

The pilings that buckled are 8 feet below the bottom of the concrete footing supporting the pier.

The investigation also found that the vast majority of the other bridge piers being checked are in the same condition as they were when installed 33 years ago. The DOT said the bridge has not moved since it settled last week and there is no danger of collapse.

"As the investigation concludes, work will get underway to consider possible repairs," Will Dorsey, northeast regional director for the DOT, said in a release. "Our goal is to do whatever is needed to quickly and safely reopen the bridge.

Pier 22 on the bridge's east side sank two feet on the morning of Sept. 25, causing the deck to sag and the bridge to be closed to traffic indefinitely.