Washington( CNN) Justice Department Special Counsel Robert Mueller has issued grand jury subpoenas related to Donald Trump Jr.'s 2016 meeting with a Russian lawyer at Trump Tower, according to a person very well known the matter.

Mueller's grand jury activity was first reported by The Wall street Journaland Reuters.

Mueller's team of investigators continue to look into whether President Donald Trump or any of his campaign associates colluded with Russia during the presidential competition.

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