Speaking at the TED Global conference, Assange said that "we are overwhelmed by our growth" and the site can't keep up with the volume of the new material because it doesn't have enough people to verify it.
He later told reporters that "there are many things which are very explosive."
Assange said the organization gets material from whistle-blowers in a variety of ways -- including via postal mail -- vets it, releases it to the public and then defends itself against "the regular political or legal attack."
He said the organization rarely knows the identity of the source of the leak. "If we find out at some stage, we destroy that information as soon as possible," he said.