Demand for further scrutiny may mean reinstalling 6.3km of cabling infrastructure on East London line

Contractors building the East London line may have to spend £600,000 reinstalling 6.3km of cabling infrastructure after Transport for London questioned its fire resistance.

It is understood that a joint venture between Balfour Beatty and Carillion has been unable to prove that the trays it has installed to carry communication and electrical cables meet the “Quensh” fire standards demanded by Transport for London (TfL).

This is higher than the Class O standards required by Network Rail for the overground.

The fibreglass troughing was supplied by manufacturer Mita; independent sources say it costs about £100 a metre to make and install.

It is not yet clear whether the product meets the Quensh standard; a source close to London Underground said Mita was unable to produce the appropriate certification when asked.

A statement from Balfour Beatty and Carillion confirmed that the product was undergoing independent testing. It added: “The supplier was requested to provide recent test results to support the quality assurance that the joint venture and TfL rightfully demand.”

A spokesperson for Mita said it took public safety seriously. She said: “We always follow appropriate process.”

A London Underground spokesperson said: “TfL and the joint venture are testing the products in question. Once testing is finished they will make a decision about what action, if any, needs to be taken.”

When complete in 2010, the £1bn project, which is being managed by Parsons Brinckerhoff, will extend the line to Highbury and Islington in the north and Crystal Palace and West Croydon in the south.