Capricornia sent this in:

Just to give you a bit of information using my Japanese language skills, the local Japanese-language Yahoo! site offered the following with regard to the death of Mitsuhara Misawa at this link (posted Monday morning in Japan): click here.

A quick translation would read like this:

“With regard to the accident that resulted in the death of the professional wrestler, Mitsuharu Misawa, President of NOAH, during a match held in Naka Ward, Hiroshima City, Hiroshima Prefecture on the 13th of June, in response to inquiries made to the Chuo Police Station of the Hiroshima Prefectural Police regarding the cause of death of Misawa, it is now known that the cause of death was a cervical cord injury.

At around 8:00pm on June the 13th during a tag-team match held at the Hiroshima Prefectural Gymnasium, Misawa was on the receiving end of a backdrop which resulted in him hitting his head very hard. Death was later confirmed at around 10:10pm on the same evening at Hiroshima University Hospital”

(reporter Daiki Hoshi).

Note from Adam Martin:
Despite a report we made earlier today sourced by The Wrestling Observer/Figure Four Online, it would appear basic inquiries for information were able to provide the cause of death.