Fifteen asylum seekers say they spent three days on Christmas Island before being turned back to Indonesia.
The six Iranians, two Nepalese and seven Bangladeshis were found off Sukabumi, West Java, on Sunday.
Sukabumi Immigration officer Irfan Sapari says the group claims Australian authorities sent them back to Indonesia on the same fishing boats they arrived on.
They say they spent three days on Christmas Island first.
"We don't know for sure what happened, but that's what they say," Mr Irfan told AAP.
"When they were there for three days, they were sheltered.
"They were given logistics, fuel and then they were told to sail back."
Sukabumi Immigration office chief Markus Lenggo told Indonesian wire service Antara the group includes three young Iranian girls.
"From the testimony of the immigrants, they reached Australia three days ago after leaving from Pameungpeuk, Garut, on March 17 and stayed there for three days," he said.
One of the asylum seekers from Bangladesh, Muhamed Baleyet Husain, told Antara the group reached Australia three days ago.
"We arrived in Australia, in Christmas Island to be exact," he said.
"But the government sent us back to Indonesia by boat, escorted by the Australians."
He reportedly spoke fluent Indonesian after living in the country for six months.
Another passenger, Kamal, was quoted by Indonesian news website viva.co.id saying they were sent back to Indonesia in two fishing boats.
"Then the boat captains who brought us left us after we reached land," he said.
Immigration authorities were liaising with International Organisation for Migration (IOM) and Indonesia's Law and Human Rights Ministry.
Of the 15 asylum seekers, nine had letters from the UNHCR declaring their refugee status but the other six said their letters were missing.
