Water sampling conducted by Bay of Plenty Regional Council has confirmed that the bloom of blue green algae in Lake Okaro, near Rotorua has worsened.

A health warning advising against recreational use of the lake has been in place since July.

The algal bloom at Lake Okaro near Rotorua has worsened.

Medical Officer of Health Dr Phil Shoemack says testing done last week shows the bloom has increased in intensity.

'Now warmer weather has arrived it is possible the algal bloom could continue for some time and people should be very cautious before using Lake Okaro for any form of recreation,” says Dr Shoemack.

Blue green algae, also known as cyanobacteria, can produce toxins, which are particularly harmful to both people and animals, especially dogs.

The toxins can aggravate asthma or eczema, result in stomach upset, and cause skin rashes, numbness and tingling.

Lake Okaro, near Rainbow Mountain, approximately twenty kilometres to the south of Rotorua, has a significant recent history of algal blooms reflecting the high level of nutrients contained in the lake sediment.

Regular testing of the lake will continue over the summer months.

For all health warning updates across the Bay of Plenty and Lakes districts call 0800 221 555. Further information is available at www.ttophs.govt.nz