The Tufts University international student who’s been held in a Louisiana detention facility since last month says she thought the plain clothes officers who detained her “were going to kill [her].”

In court filings Thursday, 30-year-old Rümeysa Öztürk for the first time described the circumstances under which she was taken by federal immigration officials — and how she’s been treated during her imprisonment.

She says when she was first approached by officers in Somerville on March 25, she didn’t realize they were law enforcement.

“Since appearing on the Canary Mission website in February, I had begun to be afraid that I could be targeted for violence,” Öztürk wrote, referencing a list maintained by a pro-Israel group. “When the men approached me, my first thought was that they were not government officials but private individuals who wanted to harm me. I felt very scared and concerned as the men surrounded me and grabbed my phone from me.”

Since arriving to a detention center in Louisiana, she alleges instances of medical neglect for her asthma, civil rights violations related to her Muslim faith and being crammed into a cell with 23 other women — in a cell that was made for 14.

“The primary thing for us right now is that we’re very worried about her health,” said Adriana Lafaille, an attorney representing Öztürk with the ACLU of Massachusetts. “Rümeysa has had 13 asthma attacks in her life — and four of them have been in these last couple of weeks that she has been detained.”

Lafaille said the best way to guarantee Öztürk’s safety is to release her.

Öztürk was heading to meet with friends to break her Ramadan fast when she was stopped near her home by masked, plain clothes U.S. Immigration and Customs Enforcement agents. She was transported to New Hampshire, Vermont — where her case is being heard — and finally to Louisiana the next day, where she is currently being held at South Louisiana ICE Processing Center in Basile.

En route to Louisiana in Atlanta, Ozturk experienced an asthma attack and used an inhaler.

“I could not get over the asthma attack,” she said. “I asked for the medication I am prescribed to treat asthma attacks but I was told that there was no place to buy it and that I would get it at my final destination.”

She described multiple other asthma attacks over the coming weeks — at least one due to the dampness in her cell — as well as instances where she hasn’t been treated despite going to a medical facility and having religious rights violated.

“Once they finally took me to the medical center, the nurse took my temperature. She said ‘you need to take that thing off your head,’ and took off my hejab without asking my permission,” wrote Ozturk. “I told her you can’t take off my hejab and she said this is for your health.”

After a few minutes, she put her hejab back on, and said the medical staff did “nothing to treat my asthma and gave me a few ibuprofen.”

Fatema Ahmad, executive director of the Boston-based Muslim Justice League, said that Ozturk’s treatment isn’t an anomaly in the ICE detention system.

“Unfortunately, this is not necessarily uncommon from what we know, both the medical treatment and the Islamophobic treatment that she’s dealing with,” said Ahmad.

Ahmad said her organization has seen the same issues play out locally at the Plymouth County ICE facility, an allegation officials there have denied.

An ACLU report last August found Muslim women detained in Louisiana ICE facilities reported repeated violations of their First Amendment rights to practice religion, alleging being told they could not wear head coverings, being forced to use towels as head coverings, not being allowed a copy of the Quran, and not having religiously compliant meals. The report also alleges poor medical treatment, little access to attorneys, and prisoners not being allowed outside for more than 30 minutes per week in the Basile facility.

Öztürk described not being able to access hygienic supplies like toilet paper for 18 hours after an initial request, depending on the correctional officer.

“The conditions in the facility are very unsanitary, unsafe, and inhumane,” she wrote. “There is a mouse in our cell. The boxes they provide for our clothing are very dirty and they don’t give us adequate hygiene supplies.”

The South Louisiana Processing center is one of nine ICE facilities in the state, and one of four run by GEO Group, a prison company that has contracted with the federal government since at least the Obama administration. GEO Group didn’t reply to request for comment about conditions at the facility and Öztürk’s claims.

Louisiana and Texas, where many immigrants from northern states are being transferred to, have the largest ICE detention populations in the country, according to Transactional Records Access Clearinghouse.

Öztürk’s case was transferred to the District of Vermont last week, after a judge in Massachusetts decided it was the best jurisdiction given Öztürk was in the state when her attorney filed a complaint in court. A hearing on Monday before a new judge could determine if she remains in ICE custody in the South.

“We really want to get Rümeysa out so that she can be safe and return to her community at Tufts, where she is beloved and where she has the opportunity to work on research and projects that are really dear to her,” said Lafaille, when asked if Öztürk could be transferred back to New England.