The NZ Defence Force has been called to a park in Nelson after explosive material was found.
A childcare centre in the area has been evacuated out of precaution and the car park of Founders Heritage Park where the explosive material was found has been closed.
The building in Whakatū Marae closest to the Founders boundary has also been evacuated.
The NZ Defence Force's Explosive Ordnance Disposal (EOD) unit is carrying out the assessment of explosive material.
Nelson City Council said the Defence Force's EOD unit was assessing items in the park's collection for picric acid.
It said picric acid was widely used in early forms of medicine and medical supplies, including on gauze pads and as an antiseptic. It is a volatile substance sensitive to heat, friction and shock, and has been used as a military explosive.
Police are also in the area surrounding Atawhai Drive while the material is safely disposed of.
Members of the public have been asked to avoid the park.
Picric acid is the same substance which saw Napier Library evacuated late last month.
Waikawa Museum in the South Island was also closed earlier this month after a "substance of concern" was found.