ISLAMABAD, Sept 4: The National Highway Authority (NHA) will hold an in-house inquiry to determine the cause of the collapse of the Shershah bridge in Karachi.

A separate committee would be formed after senior officials of the authority return from Karachi, perhaps on Wednesday, NHA spokesman Kashif Zaman told Dawn on Tuesday.

He said the committee would hold independent investigations.

The spokesman said the inquiry process had already been initiated, as evidence was being collected and relevant records taken into custody.

The names of the committee members would be announced soon, he added.

Mr Zaman, who himself is a well-known engineer, said preliminary investigations show that the bridge collapse was a design failure and not because of substandard material.

To a question, he said that passengers and transporters should not be worried about the firmness of other bridges, adding that they were safe and sound. He said the NHA had constructed about 320 major bridges and all of them were safe.

A six-member high-level inquiry committee has already been constituted on the directives of President Pervez Musharraf and Prime Minister Shaukat Aziz to fix responsibility for the collapse of the bridge.