A fire crew will be monitoring a 35-hectare scrub fire burning in swampland in North Waikato overnight.

A Fire and Emergency New Zealand services were alerted to the blaze off Island Block Rd near Meremere around 1.15pm this afternoon.

Four fire trucks, five tankers and three helicopters were called to the scene, but have since been stood down, incident commander Shane Bromley said.

The fire is not contained but is burning slowly through swampland.

Bromley said three houses were earlier being protected by fire trucks as a precaution but "are no longer threatened".

"A crew will monitor the situation overnight, and we will resume our air attack at first light tomorrow morning."