Speaking to a throng of reporters outside the office, he said Klein had been cooperating in the investigation. Craig Harvey, the coroner's chief of operations, says it's the second time coroner's investigators have served Klein a subpoena.
They are focusing on the role drugs played in causing Jackson's death.
Klein has recently given TV interviews saying he sedated Jackson for medical procedures. He denied ever giving the pop star an unnecessary dose of drugs.
Related Content from AccessHollywood.com:
VIEW THE PHOTOS: The Jackson Family
PLAY IT NOW: Michael Jackson's Dermatologist, Arnie Klein, Speaks Out (July 8, 2009)
PLAY IT NOW: Michael Jackson's Former Publicist Speaks Out (July 9, 2009)