WELLINGTON, New Zealand -- A mass of small volcanic rocks nearly the size of Belgium has been discovered floating off the coast of New Zealand.

The stretch of golf-ball-size pumice rocks was first spotted this week by a New Zealand air force plane about 1,000 kilometres northwest of Auckland.

The rocks stretch for about 26,000 square kilometres.

A navy ship took scientists to the rocks Thursday night. Naval Lt. Tim Oscar says the rocks appeared a brilliant white under a spotlight, like a giant ice shelf.

Scientists say the rocks likely spewed up in an eruption by an underwater volcano.

They don't believe the eruption is connected to the onshore ash eruption this week of another volcano, Mount Tongariro.

Officials say the small rocks pose no danger to shipping.