is set to open in a few months.

But India's Prime Minister, Narendra Modi,

says it doesn't even exist …

… well this one is real.

And we went to the remote northeast corner of India

to see it for ourselves.

State officials and workers told us

this compound will house up to 3,000 detainees — people who

are declared foreigners.

Reporter: “Why are the walls so high?”

But here's the thing: Many of the people

likely to be held here might not even

be foreigners at all.

The fear is that most of them will be Muslim.

And the state they live in is leading Modi's push

to change India into a more overtly Hindu nation.

Monavra Khatun is Muslim.

She says she was born and raised in India,

and has the documents to prove it.

Still, she was left off a roster of Indian citizens

in Assam.

Now, she must prove she's legal

or risk being sent to detention.

She's not alone.

Almost two million people were left off that list.

Soon, many will be called to a court like this one called

a Foreigners Tribunal.

These people have been marked as suspected foreigners.

They're bringing their documents to an official.

That person, appointed by the government,

will then decide if they're Indian citizens

or foreigners.

Mamoni Rajkumari was one of those officials.

She issued decisions in over 600 cases,

the majority she found, were Indian.

And then —

She sued the government and told us

she was fired because she didn't declare

enough Muslims as foreigners.

But it was implied.

We found five more officials, like Rajkumari,

who accused the state of targeting Muslims.

Only one other would appear on camera.

The rest feared reprisal.

Kartik Roy said he started to face pressure a few years ago

when Modi's party, the B.J.P., took control in Assam.

When he didn't declare more Muslims as foreigners,

he said, he too was fired.

But how can someone with documents

who's lived for years as a citizen suddenly

be declared illegal?

Take Azbahar Ali.

This spelling error became grounds

for questioning his citizenship.

He lost his case at the Foreigners Tribunal,

and ended up going to jail for almost four years.

During that time, his family sold their land

to pay legal fees.

And his wife committed suicide.

Ali was released on bail.

But until he can convince the court that he's Indian,

his name will not appear on the citizenship list.

So he could end up back in detention.

And that list: It's riddled with clerical errors.

This man, Dukhdam Das, is also not on the list.

His case is pretty much identical to Ali's,

except for one key thing,

he's Hindu.

And as far as many in Modi's party are concerned,

that just means Indian.

So in December, the government doubled down.

It passed a new citizenship law

favoring all major religions in South Asia except Islam.

In Assam, that means Hindus who

are left off the botched list could

have their rights restored.

But across the country, critics

see the new law as the latest example

of Modi's anti-Muslim agenda.

Protests led to religious riots in India's capital.

More than 50 people died in the violence,

the majority of them Muslims.

But despite months of protesting,

Modi has not backed down.

In fact, officials in his government

have promised to make a country-wide registry

of citizens just like the one in Assam.

Modi has denied that that's his plan.

Asbahar Ali voted in the past, as only a citizen can.

But he may not get to exercise that right again.