On the main Refugees International website you can find the page that contains these numbers.

Humanitarian Crisis in Colombia: Impossible to Deny the Evidence http://www.RefugeesInternational.org/blog/humanitarian-crisis-colombia-impossible-deny-evidence

Colombian government figures are reporting over 2.9 million people registered as internally displaced persons as of February 28, 2009. And recently, a high-level Colombian official admitted to me that around 30 percent of displaced people do not seek registration for fear of reprisals or lack of knowledge of the process. There are also over 500,000 Colombians who have fled the country altogether.