Two Australians are potentially among seven missing after a Thai boat bound for Phuket capsized and sank after heavy rain and winds on Sunday night.

But confusion has arisen after the Austrian Foreign Ministry said that two of their nationals, Mr Klaus Konradder and Ms Monika Schuster, are missing, contradicting earlier media reports.

Choke Somboon 19, operated by Dive Asia, was travelling at speeds of eight to nine knots on its return journey when it sank from the Similan Islands to Phuket with 30 passengers and crew on board.

“23 of our guests and crew were able to get into the life rafts and have safely returned to Phuket,” reports Dive Asia in a statement.

“Seven people are still missing and a search in the area was conducted [Monday] and will continue on Tuesday morning.”

It is believed that the six-month old ship hit a vortex which had formed quickly, causing it to capsize. Local fisherman, who were nearby, raced to the scene and found the survivors adrift in an inflatable lifeboat.

Other tourists still missing are believed to be two Swiss nationals, a German national and a Japanese national.  One crew, a Thai national, is also still missing.

Additionally the Thai Navy has dispatched a boat and a helicopter to aid in the search efforts.

Dive Asia were unreachable for comment this morning.

UPDATE: Speaking to e-Travel Blackboard, the Tourism Authority of Thailand (TAT) has confirmed that it is in fact two Austrian nationals, not Australian nationals, who are currently missing.

“There was one Australian involved in the incident but he’s fine.  It’s two Austrians who are missing,” said a spokesperson.

“There were 15 tourists on board the boat... and 15 crew members,” he continues.  “We can confirm that seven are still missing.”

“They’re still searching for them.”