Immigration Minister Scott Morrison says most of the 157 asylum seekers brought to the Australian mainland are economic migrants, and Indian officials are preparing to establish their identities.

The asylum seekers, who were detained at sea on a Customs ship for weeks, are now at the Curtin detention centre in Western Australia after being flown from Cocos Island on Sunday.

They are now undergoing initial checks and assessments.

Consular officials from India, which has agreed to take back its citizens and will consider taking Sri Lankan nationals who are Indian residents, are on their way to the centre to conduct identity checks.

Mr Morrison said the government decided to bring the group to the mainland because identity checks would have taken too long on the ship.

The asylum seekers, including children, had been detained since their boat was intercepted 27km from Christmas Island earlier in July.

Mr Morrison said based on initial discussions with those on board, a majority are believed to have been long-term residents of the “safe” nation of India.

“They haven’t come from Sri Lanka, they haven’t come from any of those other countries, Afghanistan or anything like that,” Mr Morrison told ABC radio on Monday.

“A passage to Australia here is nothing more than an economic migration seeking to illegally enter Australia.”

None in the group has yet made protection claims in Australia, and most of them, where it is possible, will be sent back to India.

Mr Morrison questioned suggestions that the asylum seekers were fleeing persecution from India.

“If we can’t take people back to India, what is next? New Zealand?”

Mr Morrison denied the government had offered any sweeteners to the Indian government to get its involvement.

The decision to bring the group to land pre-empts a High Court challenge against their detention at sea.