There are concerns gas fitting work is being carried out in Auckland by unqualified tradesmen.

The Plumbers, Gasfitters and Drainlayers Board is trying to track down some gas fitting certificates it has issued.

Board chairwoman Hazel Armstrong says certificates have been bought from the board, but have not been returned.

She says the board is concerned that the certificates may have been given to other people who may not be qualified and who have gone on to do gas fitting.

Ms Armstrong says gas work done by an unlicensed gas fitter is not covered by insurance and needs to be checked.

She is urging Auckland homeowners who have recently had gas fitting carried out to check their certificates.

The certificate numbers can be checked against those listed on the board's website.