Online retailer Amazon is being investigated by the British record industry in a probe into cheap CDs.
Amazon is one of the web's success stories
The British Phonographic Industry (BPI) is looking into whether it breaks UK laws by selling cut-price music.
The BPI said it was questioning as routine whether Amazon was selling CDs obtained outside the European Economic Area, contravening UK law.
It is already suing retailers CD-Wow and Play.com for allegedly sourcing music from cheap overseas suppliers.
Amazon is one of the most successful online retailers, intially known for selling books it has diversified into other markets including music, with the average price of a CD under £10 and some as low as £5.
A BPI spokesman said: "This is a standard routine. We look at many websites to determine if the product is legitimate.
"If we find a net retailer is importing music from outside Europe, then they are infringing copyright law."
Many web retailers have built up their businesses by offering CDs considerably cheaper than high street shops.
But there is a concern that products are being brought in from areas such as Asia, therefore bypassing import laws.
Online sales have helped revive a struggling music econony with increased album sales, although the market saw a 7% drop in profits last year.