The Kopu Bridge on State Highway 25 has re-opened after it was closed for several hours to check out an issue with the bridge's opening span.

Traffic from Thames to Auckland or Auckland to Thames was diverted via Paeroa.

NZTA Acting State Highways Manager Hamilton Michelle Te Wharau says the bridge re-opened just before 7pm, after being closed as a precautionary measure at 1.45pm this afternoon.

The Kopu Bridge. Image: Google Earth.

Traffic between Auckland and Thames was diverted via Paeroa.

NZTA Acting State Highways Manager Hamilton Michelle Te Wharau says the bridge re-opened just before 7pm, after being closed as a precautionary measure at 1.45pm this afternoon.

The closure was necessary to inspect the bridge and carry out repairs after contractors working on the new Kopu Bridge noticed a fault with the swing span section of the bridge.

Detours were immediately put in place for traffic travelling in the area, whilst an assessment was carried out by engineers.

"We want to reassure the public that the bridge remains structurally sound. The fault detected today was caused by a bolt failure on a steel plate which bridges a 100mm gap between the swing span section of the bridge and the main deck. A new plate was fitted to enable the bridge to re-open to traffic as soon as possible.

"We would like to thank motorists for their patience and understanding while we worked quickly to resolve this issue," Mrs Te Wharau says.

The replacement Kopu Bridge project remains on target for completion by mid 2012.

Construction of the $47m two-lane Kopu Bridge was brought forward in 2009 as part of the Government's $500m Jobs and Growth Plan. It will replace the existing one-lane bridge built in 1928. Once completed, the new 580m-long bridge will reduce traveling times for all bridge users.

The Kopu Bridge is, at 463m the longest single lane bridge in the country and is controlled by traffic lights.

The centre span can still open to provide a 15 metre wide channel for shipping that may wish to travel upstream.

The bridge carries an average of 9000 vehicles per day.