A fraud-hit Welsh slate business has been sold for £31m, it has been announced.

Alfred McAlpine has sold the north Wales operation to Rigcycle a company linked to construction group Lagan.

It is understood workers at quarries in Penrhyn, Blaenau Ffestiniog, Cwt-y-Bugail and Penyrorsedd, will transfer to the new owners.

McAlpines uncovered what it described as "clear and systematic fraud" within the business earlier this year.

The company, which supplied slate to Buckingham Palace, warned the discovery was set to leave it with a bill of more than £40m in lost profits and investigation costs.

McAlpines first revealed in February that it had uncovered evidence of "systematic misrepresentation" of production volumes and sales for several years by a number of senior managers at the business, who have since been sacked.

Around 140 jobs were also lost.

The company, which called in North Wales Police in April, added that those involved tried to conceal their actions by pre-selling material at much cheaper prices.

Patrick McNaught, the T&G union's regional industrial organiser, said he had heard that all the workers at the four quarries would transfer to the new owners.

Since the fraud was uncovered, Alfred McAlpine has agreed to be bought by larger rival Carillion for £572m.

The tie-up with Wolverhampton-based Carillion will form one of the largest construction and support services firms in the UK.

Rigcycle is controlled by members of the family which owns the Belfast construction group Lagan.