Maritime New Zealand has lifted a ban on swimming at Mount Maunganui's main beach in the wake of the oil spill from the grounded container ship Rena.
A section of beach between the Mount and Tay Street was re-opened on Friday but holiday makers were still told to avoid the water.
Maritime New Zealand says public health officials have now confirmed it is safe to swim, as long as people stay alert for any sign of contamination.
It says there have been no significant oil leaks from the stranded ship for 12 days and the oil that remains in the water is less toxic than fresh oil.
Maritime New Zealand says anyone who sees or smells oil should leave the water immediately.
The rest of Mount Maunganui beach from Tay Street to Maketū remains closed.
Tests on oil composition
Scientists at Waikato University are testing oil from the ship to try to determine how long it could take to break down.
Professor Alistair Wilkins says the scientists have collected oil from the Rena's tanks, from slicks on the surface and from tar balls found on Mount Maunganui beach.
He says they are looking at how its chemical composition has changed.
Professor Wilkins says once they have more information on the compounds involved they will be able to work out how long the oil is likely to take to degrade and when it will be safe for shellfish to be consumed again.
He says he can not predict how long the testing will take.