Dag Kittlaus, the co-founder and CEO of Siri, whose voice control feature Apple launched to much acclaim recently, left the company, according to sources.

There were several reasons for the departure, which was amicable and was planned for a while, sources said. They included Kittlaus' family being in Chicago, a desire to take time off and an interest in brainstorming new entrepreneurial ideas, AllThingsD reported.

Kittlaus has led the speech recognition efforts for Apple since it bought Siri in April of 2010. He had been Siri's CEO since 2007. Before that, the Norwegian-born Kittlaus was an entrepreneur in residence at the Stanford Research Institute and also worked at Motorola.

Kittlaus apparently left after the launch of Siri, but sources said other key Siri execs were expected to remain at Apple.

Apple did not immediately respond to a request for comment.