Staff at a north Wales slate works are being warned compulsory redundancies are likely because new machinery will mean fewer workers are needed.

Welsh Slate, which has its main operation at the former Penrhyn quarry in Bethesda, has started briefing staff about the changes.

The managing director said it was not clear when jobs would go, or how many redundancies would be involved.

The company employs around 240 people in Gwynedd.

The firm is bringing in new machinery and plant, which means fewer workers will be needed at the quarry.

In April, Welsh Slate announced it was asking staff to accept a 10% pay cut because of the slowdown in the construction industry.

In August last year, the company announced it was cutting 50 jobs because of the global economic downturn.

The quarries were bought from previous owners Alfred McAlpine for £31m two years ago following the discovery of a large-scale fraud within the business which McAlpine said would leave it with a bill of more than £40m in lost profits and investigation costs.

It was taken over by Rigcycle, a company run by the Northern Ireland construction company Lagan.

Welsh Slate operates four quarries in Bethesda, Nantlle and Blaenau Ffestiniog for roofing slate, aggregates and architectural products.

The company reported a turnover of £27m in 2008.

The owners believe Penrhyn quarry has enough reserves for more than 25 years, and have said that in combination with the reserves at Welsh Slate's other three quarries, it will underpin the company's production for many years to come.