Indonesian maritime police detained 50 Vietnamese bound for Australia on a boat last Saturday, with the Jakarta Globe newspaper calling them "asylum seekers."
The 47 men and three women were found in weak condition aboard an Indonesian-flagged wooden boat in Alas Strait.
Local police suspect they had been at sea for 14 days.
The immigrants were taken to a port and put in a hotel. The police have been assessing their health since many looked weak and exhausted.
They would soon be moved to a police detention center, the police said.
One of the Vietnamese, Tran Van Gion, who police suspect may have skippered the boat, was questioned, the newspaper said.
This is the fifth time that Australia-bound illegal immigrants have been seized in West Nusa Tenggara this year, the police added.
Usually the Indonesian police hand them to the local immigration office.