Many new houses and blocks of flats have been built in Cardiff Bay

Cardiff-based A & A Property had more than 250 houses and flats on its books in different areas throughout Wales.

It is the first big casualty in the Welsh housing market since the start of the credit crunch, says BBC Wales business correspondent Nick Servini.

The National Association of Estate Agents in Wales believes more could go under as banks harden lending policies.

Like everywhere else in the UK, the buy-to-let property market has been booming in Wales in recent years.

I think it was bound to happen because there has been a great deal of investment in property over the past three or four years, particularly within the Cardiff area Michael Jones, estate agent

A & A Property has been by hit by serious financial difficulties and administrator Grant Thornton has been called in.

Michael Jones, director of the Michael Jones Estate Agents in Cardiff, said the news came as no surprise.

"People who've bought at the top of the market and suddenly find that prices are falling, and of course there is a hole in their funding and the banks are starting to get very nervous about it," he said.

"With those numbers that [the company has] been buying, that's a huge amount of money.

Speculating

"If you're looking for big returns both in rental and capital value and suddenly hit the buffers, that's very bad news for them."

"I think it was bound to happen because there has been a great deal of investment in property over the past three or four years, particularly within the Cardiff area.

"With the development of [Cardiff] Bay, there have been a lot of people buying and speculating, and that bubble does appear to have burst.

"I'm aware of some huge investments by national and international companies and they are struggling to reach their targets.

"We've overdeveloped certain areas and built the wrong type of properties. The credit crunch has put the top hat on it."

He advised individuals who had put savings into buy-to-let properties to watch the market and "sit tight".

"There is still a rental market. As long as you are sensible with your rents, you will let these properties."