India has made a diplomatic protest to the US after 129 Indian students were arrested for enrolling in a fake university.
The University of Farmington, advertised as based in Michigan state, was run by undercover agents from the Department of Homeland Security to expose "pay-to-stay" immigration fraud.
Prosecutors say those who enrolled knew that the facility would be illegal.
However, Indian officials say the students may have been duped.
On Saturday, the Indian Ministry of External Affairs (MEA) issued the protest to the US embassy in Delhi, expressing concern over the arrests and demanding consular access to those detained.
"Our concern over the dignity and wellbeing of the detained students and the need for immediate consular access for Indian officials to the detainees was reiterated," the ministry said.
How were students lured?
The fake university was set up in 2015 to try to catch foreign nationals who had initially travelled to the US on student visas and wanted to stay in the country, US media reported.
A website for the University of Farmington showed pictures of students in classes and libraries, or relaxing around a grassy campus.
It advertised tuition for undergraduates at $8,500 (£6,500) a year and $11,000 a year for graduate students. It also had a fake Facebook page with a calendar of events.
But court papers released last week showed that the employees of the University of Farmington were undercover agents for the Immigration and Customs Enforcement agency (ICE).
The "campus" was an office at a business park in a Detroit suburb.
Who is being accused of what?
The indictment, filed in the District Court for the Eastern District of Michigan, said the students knew the scheme was illegal.
Prosecutors say the spurious university was being used as a "pay to stay" scheme - allowing people who entered the country legally as students to extend their stay and work by transferring to it.
A total of 130 students - including 129 from India - were arrested on Wednesday and charged with civil immigration charges, the Detroit Free Press reported.
The students face possible deportation if convicted.
Separately, eight people who allegedly acted as recruiters were charged with conspiracy to commit visa fraud and "harbouring aliens for profit".
What is India arguing?
The Indian government said the students could have been tricked into enrolling.
"We have urged the US side to share full details and regular updates of the students with the government, to release them from detention at the earliest and not to resort to deportation against their will," MEA added.
Some immigration advocates in the US also believe innocent foreigners were trapped by the government.
Ravi Mannam, an immigration attorney in Atlanta, told the Detroit Free Press that the sting "kind of hooked these students by promising them credits for their previous master's programmes".
Meanwhile a telephone hotline for worried relatives of those being held has been set up at the Indian embassy in Washington, the Times of India reported.
The US embassy in Delhi confirmed it had received the note of protest but made no further statement.
What is behind the crackdown?
US immigration authorities have resorted to increasingly tough enforcement tactics in recent years.
In a precedent to the latest sting, immigration agents set up the fake University of Northern New Jersey in 2016 under the Obama administration. A total of 21 people, mostly from China and India, were arrested.
Over the past two years, the Trump administration has further clamped down on undocumented migrants and visa overstayers.
Workplace raids have led to hundreds of arrests.
In two massive operations last year, ICE agents detained 146 people at a meat supplier in Ohio and another 150 at a trailer manufacturer in Texas.