(CNN) When 64-year-old Kamyar Samimi died in ICE custody, the agency issued a routine press release saying the preliminary cause of his death was cardiac arrest. It boasted about the nearly $200 million it had been spending annually on health care services for detainees, saying that "comprehensive medical care is provided from the moment detainees arrive and throughout the entirety of their stay."

What the press release didn't say was that Samimi's death followed a series of lapses in his medical care -- the sort of breakdowns that have been repeatedly identified in government investigations into the care provided at immigrant detention centers in recent years.

Samimi, an Iranian man who was being held by ICE in Aurora, Colorado, had been complaining of vomiting and pain for weeks leading up to his death in 2017, according to ICE's investigation into his treatment. He had told medical staff upon his arrival that he had been taking methadone, a painkiller commonly used to treat opioid addiction, since hurting his back in a car accident. He said he was starting to feel symptoms of withdrawal, yet nurses told investigators they didn't have training in opioid withdrawal.

ICE's report, which involved an outside analysis of his treatment and like other death reviews did not directly connect the medical failures to the death, also found that the facility had been without a director of nursing and another medical provider for more than six months. Around a week before Samimi died, he was found unconscious on the floor of his cell but wasn't sent to the hospital. And on the day he died, a nurse tried calling the doctor multiple times for help after the inmate appeared to have suffered a seizure, but the doctor didn't answer or return any of those calls.

What should we investigate next? Email Blake Ellis and Melanie Hicken

Investigations into deaths including Samimi's, as well as critical government audits, have raised troubling questions about the quality of medical care at facilities used to hold immigrants. One of the main private contractors providing health care in these facilities, which employed the doctor in the detention center where Samimi was held, is a massive company known as Wellpath, formerly Correct Care Solutions.

This company was the focus of a recent CNN investigation that exposed how it has provided substandard care that has led to deaths and other serious outcomes that could have been avoided. Through records and interviews with current and former employees, CNN showed how the company has relied on inexperienced workers, offered minimal training and understaffed facilities -- and how its employees have failed to get inmates the emergency care they needed.

Wellpath also works in some of the country's largest detention facilities, where ICE locks up thousands of immigrants -- many of whom have been apprehended for entering the country illegally.

In addition to at least five death reviews conducted by ICE that specifically cite issues with the contractor's treatment of immigrant detainees, a recent class action lawsuit spotlighted the company's problematic record -- calling the decision to hire medical contractors such as Wellpath "disturbing." In the suit, more than a dozen current detainees at a variety of detention centers accuse ICE of violating the US Constitution by denying them adequate medical care and failing to provide stronger oversight.

ICE did not comment on Wellpath, but in response to the lawsuit an official said that "all ICE detainees, regardless of location, can expect timely and appropriate responses to emergent medical requests, and timely medical care appropriate to the anticipated length of detention."

Wellpath did not comment on the lawsuit or government findings about specific detainees and facilities, but said in a statement that it is confident its "team made the best possible care decisions with the information that was available to them."

"Our compassionate team of doctors, nurses and health care providers work with our partners to deliver high quality health care in a clinical environment where security is the highest priority," the company said.

Private contractor GEO Group operates a number of the immigrant detention centers where Wellpath provides medical care, and it employed the nurses and other medical staff at the facility where Samimi died. The company declined to comment.

One of the class-action plaintiffs, Martín Muñoz, has Type 2 diabetes and has been detained at the Adelanto ICE Processing Center in California -- where Wellpath is the medical provider -- for more than two years. He alleges in the suit he was given more than triple his regular dose of insulin, resulting in an overdose. He says he wasn't seen by a doctor after the overdose, and that there have been multiple occasions where he hasn't been given his insulin or blood pressure medication.

The lawsuit states he went without insulin for six days in February and 10 days this summer, without blood pressure medication for two weeks in the spring and without cholesterol medication for a week in July. Muñoz, who has lived in the United States for more than 40 years, most recently worked as a handyman and has four children who are US citizens.

Another current detainee at the Adelanto facility alleges he lost vision in one eye when a recommended surgery wasn't provided, while a man held at California's Mesa Verde immigrant detention center -- where Wellpath is also the medical provider -- claims in the lawsuit that he has received no treatment for a severe parasite in his brain.

At least 27 people have died while being held in ICE custody since 2017, according to the Southern Poverty Law Center, one of several advocacy organizations involved with the suit. An ICE official said in a statement that "statistically, fatalities in ICE custody occur approximately 100 times less often (than) they do in both federal and state custody nationwide."

Lawmakers who have previously criticized the conditions and medical care at ICE facilities have also expressed serious concerns to CNN about Wellpath.

"The reports of widespread and sometimes deadly deficiencies in the medical care provided by Correct Care Solutions ... are deeply troubling," said Sen. Kamala Harris, D-California, in a statement provided to CNN. "The United States government has a moral obligation to respect the dignity of every individual in its care, and that mission is severely compromised when government agencies transfer responsibility to private corporations incentivized to cut costs and turn profits."

In December 2018, Harris and a group of other California lawmakers wrote a letter to ICE , condemning the agency for the "egregious violations" identified during an inspection of the Adelanto detention center.

In its 2018 report, a Department of Homeland Security watchdog said it had found that detainees did not "have timely access to proper medical care" and that doctors were indicating they had seen patients they didn't actually visit. ICE said at the time that it takes the findings seriously and would be conducting a review to ensure standards are now being met.

"We must ensure that migrants in our custody are treated with the care and respect they deserve," Rep. Scott Peters, D-California, told CNN. "Wellpath must be appropriately investigated, and should not be awarded any contracts until such an investigation has been completed."

Colorado Rep. Jason Crow said he has similar concerns about the medical care at the immigrant detention center in his district, the Aurora facility where Samimi died.

The ACLU of Colorado recently released a report condemning Samimi's medical care, saying that the doctor "made the medically unjustifiable decision to cut him off from his prescribed methadone." Samimi had even called a friend and told him he was "sicker than hell" and "dying here," according to the death review obtained by the organization and Rocky Mountain PBS

The ACLU is currently suing ICE in an attempt to get more records about what happened.

"ICE arrested a man who had lived in the US for over four decades, and 15 days later he died in ICE's care," the ACLU said in a statement about Samimi's death. "The public deserves to know more."

Do you have information to share? Email us at watchdog@cnn.com.