A Melbourne woman bound for a holiday in the United States claims she was strip-searched, locked up in a federal prison and sent back to Australia by border officials.

Molly Hill left Australia for Honolulu on Monday on a tourist visa with a return flight and on arrival was whisked into an interrogation room, she says in a Facebook post on Thursday.

Molly Hill says she was detained in Hawaii after US border officials suspected her of planning to immigrate illegally. Credit:Facebook/molly.hill.5492

Ms Hill says her luggage was searched and immigration officials told her they understood she had an American boyfriend.

They searched her personal diary during an alleged six-hour interrogation and concluded she was going to stay in the US illegally.