Facebook has removed 5,500 sex offenders from its social networking website since May last year.
It follows news from Myspace that it had removed 90,000 sex offenders from its website in the last two years.
The two websites were asked by a US attorney general to implement a range of safeguards, including better ways to verify users' ages and limiting older users' ability to search the profiles of those under 18, the Associated Press reported.
Facebook said it had found the offenders through a mixture of user reports, working with law enforcement agencies and using the national sex offenders' register.
Facebook's chief privacy officer said the company has proposed a system in the US that will check available outlets in real time to block sex offenders at the beginning of the registration process. At the moment, the policy is to remove offenders when they are identified.