Tsunamis may strike Hawaii early on Friday after a huge earthquake in a remote area between New Zealand and Tonga.
The magnitude 8 quake, which has already prompted evacuations in New Zealand, struck the Kermadec Islands region at 9.28am (7.28pm) Hawaii time.
The Pacific Tsunami Warning Center said it is investigating whether the event poses a threat to Hawaii.
If tsunamis are generated, the first waves would reach the Hawaiian Island chain at 4.35pm – which would be after just after midnight UK time.
The agency issued a tsunami warning for American Samoa but then downgraded it to an advisory.
A warning means tsunamis with the potential to generate widespread inundation are expected or occurring.
The powerful magnitude 8.1 earthquake struck in the ocean off the coast of New Zealand – which is a day ahead of Hawaii – on Friday, prompting some evacuations and tsunami warnings across the South Pacific.
It was the second large quake to strike within hours.
An offshore magnitude 7.3 quake had awoken many people during the night throughout New Zealand. While both quakes triggered warning systems, neither of them appeared to pose a widespread threat to lives or major infrastructure.
Civil defence authorities in New Zealand told people in certain areas on the East Coast of the North Island on Friday morning that they should move immediately to higher ground and not stay in their homes.
They said a damaging tsunami was possible.