A corruption inquiry at Auckland Transport has widened as a manager under suspicion has gone on sick leave.

The senior staff member is one of at least three Auckland Transport employees to have their computers seized as part of an internal inquiry into roading contracts.

The Serious Fraud Office is poised to step in. The usual $2-million threshold for an SFO inquiry would not be required due to the high public interest, a spokeswoman said.

Auckland Transport manager Murray Noone was fired last week after an internal investigation found "serious conflict-of-interest and performance issues".


Noone was running a private consultancy business, Preside Consulting, while working for Auckland Transport.

Auckland Council member Wayne Walker said serious questions around contracts to large contractors had been raised. "The tendering process is increasingly shutting out the small and medium-size players," he said.

Walker, a former Rodney district councillor, said a laissez-faire culture that existed at Rodney had moved to Auckland Transport.

Auckland Transport communications manager Wally Thomas said the investigation into corruption allegations was likely to be wrapped up in weeks.

Meanwhile, Aucklanders trying to halt chemical spray claim Auckland Transport officers stonewalled their attempts to get information on weedkilling contracts.

Hana Blackmore, of the Weed Management Advisory, wants the corruption inquiry to also review road corridor vegetation control contracts and costings.

She said Auckland Transport officials produced figures showing it would cost 800 per cent more to use non-chemical treatments to kill weeds.

"Auckland Transport has not only continued to deny us the basis and evidence for these costings, but has perpetuated their claims in operational policy going through council at this moment."