Police are investigating the death of a 15-month-old Greymouth boy.

Leith Hutchison was rushed to hospital three weeks ago in cardiac arrest.

A bleed on his brain was later identified by medical staff.

The results of the post mortem examination aren't expected back for several weeks.

Some of the testing has been sent overseas for analysis.

Meanwhile police are continuing to put together the pieces of the puzzle.

They've been trying to establish whether an assault took place in the lead up to the child's death.