Sullivan (far right) played at the Download Festival in 2006 with his band

James "The Rev" Sullivan, drummer for US heavy metal band Avenged Sevenfold, has died aged 28.

Sullivan, who co-founded the band in 1999, apparently died of natural causes at his home in California on Monday.

A statement on the band's website said Sullivan was "one of the world's best drummers, but more importantly our best friend and brother".

Avenged Sevenfold played the Reading and Download festivals in the UK. Their last album charted in the US top five.

The band picked up a Kerrang! magazine album of the year award in 2008 for their self-titled LP, and were currently working on their fifth studio album.

The statement added: "Jimmy you are forever in our hearts. We love you."

An autopsy performed on Sullivan on Tuesday was inconclusive as to the cause of death.

Orange County sheriff spokesman Jim Amormino said the coroner's office has ordered toxicology, microscopic and laboratory tests to help determine why the drummer died.

It is expected to be several weeks before the results are known.