As many as 20 marines could face criminal or disciplinary actions after investigation into the death of a Muslim recruit from Michigan found a multitude of policy and procedural violations, including alleged physical and verbal abuse by drill instructors.

The US marine corps found “recurrent” physical and verbal abuse of recruits by drill instructors, officials said on Thursday, as part of three internal investigations into the death of 20-year-old Raheel Siddiqui. And a drill instructor previously under investigation for allegations of assault and hazing was also improperly assigned, officials said, while commanders had “gaps” in awareness of their roles within an investigation process.

A number of commanders and senior enlisted advisers were fired, and a number of drill instructors have been suspended, as a result of the investigations, according to a statement by the US marine corps.

“I fully support and endorse these initial actions,” said Gen Robert Neller, commandant of the marine corps, in a statement.

Siddiqui, a high school valedictorian from suburban Detroit, is believed to have fallen three stories to his death, in what the military classified on Thursday as a suicide. The Wall Street Journal, citing unnamed marine officials, reported that Siddiqui leapt from the balcony of a barracks building at the marines recruit depot at Parris Island in South Carolina, after a drill instructor slapped him in the face. A copy of the investigations were not immediately available, and a spokesperson for the marines could not be reached for comment.

From the outset, family members and lawmakers raised questions about whether hazing played a role in Siddiqui’s death. US congresswoman Debbie Dingell said on Thursday the announcement of possible disciplinary action marks the “first step in ensuring the family of Private Raheel Siddiqui receives the answers they deserve and that the marine corps is addressing the serious issues that led to this tragedy”.

Dingell said investigations into alleged abuse and mistreatment are critical to ensure “all those who are responsible are held accountable”. She said she plans to visit the recruit depot at Parris Island this weekend to witness firsthand the recruit training process and learn about new changes being implemented.

The family met marine officials who provided a copy of the report, officials said. The Wall Street Journal reported that results of the investigation will be reviewed at a hearing – possibly in the coming weeks – to decide whether administrative or criminal proceedings will commence.

A drill instructor involved in Siddiqui’s incident was already under investigation for alleged mistreatment of another recruit, having reportedly forced the individual into a clothes dryer in the laundry room. The Journal reported that the instructor accused the recruit of participating in the 9/11 terrorist attacks, before switching on the machine.

The drill instructor was suspended and returned to duties before Siddiqui arrived in March. Officials told the Journal that Siddiqui, days after training began, sought medical attention from the instructor, who denied him care and forced him to run across the barracks floor several times. Siddiqui began to cry, the officials told the newspaper, and collapsed on to the floor, appearing unresponsive. The drill instructor then slapped Siddiqui, prompting the recruit to get up and run over the railing of a stairwell, where he fell to his death.

Shiraz Khan, an attorney for Siddiqui’s family, said in a statement the investigations’ findings are being reviewed by family members to determine the “next course of action.”

“At this time we acknowledge the efforts of the United States Marine Corps,” Khan said. “However, there are too many questions that remain unanswered. We will work with NCIS as they move forward with their investigation.”

“When America’s men and women commit to becoming Marines, we make a promise to them,” Neller said in the statement. “We pledge to train them with firmness, fairness, dignity and compassion. Simply stated, the manner in which we make Marines is as important as the finished product. Recruit training is, and will remain, physically and mentally challenging so that we can produce disciplined, ethical, basically-trained Marines.”

“We mourn the loss of Recruit Siddiqui,” he continued, “and we will take every step necessary to prevent tragic events like this from happening again.”