David McLean employs 320 people with offices in Cardiff and Shrewsbury
The debts of a building company which is in administration are likely to run up to £100m.
Nick Edwards, joint administrator with Deloitte, revealed the debt figure for Flintshire-based David McLean Holdings Ltd and said there would be job losses.
The company employs 320 workers and went into administration on Monday as a result of the recent property downturn.
Mr Edwards said he hoped to sell the housing side of the business as a going concern to help minimise job losses.
Meanwhile, North Wales Police said a major £2.5m refurbishment of its Colwyn Bay headquarters would be delayed because of the problems surrounding contractors David McLean.
Work began last November and was due to be completed by the end of the year.
"Our aim is to get the contract up and running as quickly as possible in association with the main sub-contractors and we will work closely with the administrator to ensure this," said a force spokesman.
The David McLean group was founded in 1972 and has offices in Cardiff and Shrewsbury with a turnover of £160m.
However, the joint administrator confirmed that its housing, contracting and development divisions were all in administration as a result of various market conditions.
Mr Edwards said the contracting division will close with subsequent job losses but hoped the housing division could be sold as a going concern.
Asked about the level of debt the company had run up, Mr Edwards told BBC News: "It will run into many millions, I would say, getting towards £100m.
"The group in the previous 12 months until the end of June sold just under 600 units - homes and apartments - and there are about 30 sites around the UK - primarily the north west, midlands and south Wales and the south west - which are at different stages of development.
"There will be a number of job losses, there already have been a number of job losses.
"A lot of it comes down to if we have the ability to sell the homes business as a going concern to preserve jobs.
"The contracting business is a matter we're going to have to deal with."
The McLean group's Deeside headquarters employs 130 staff with another 40 in Cardiff, 25 in Shrewsbury and 105 working out on location.
As well as the police headquarters contract, it has another building contract involving Prestatyn School and 11 housing developments across Wales.