A second person's been poisoned by the toxic algae in Lake Hood, near Ashburton

Local Democracy reports Health New Zealand issued a warning about toxic algae bloom in the lake almost two weeks ago.

A swimmer was poisoned before the warning was in place.

Symptoms can include skin rashes, stomach upsets, and neurological effects such as tingling around the mouth, headaches, breathing difficulties and visual problems.

National Public Health Service medical officer of health Dr Cheryl Brunton says another person was poisoned, after falling into the lake while jet-skiing last week.

The warning hasn't closed Lake Hood, but Brunton says people should avoid it.