The world’s biggest tantric yoga school, which closed after multiple women alleged rape and sexual assault, has reopened with the accused leader back in charge and amid accusations that management suppressed an investigation into the abuse.

Agama Yoga, which is located on the Thai island of Koh Phangan, shut down for “restructuring” in September after the Guardian published allegations by 14 women accusing the school of facilitating rape, sexual assault and misogynist teachings at the hands of its leader, Swami Vivekananda Saraswati, a Romanian whose real name is Narcis Tarcau, for 15 years.

Sixteen former pupils and staff told the Guardian they thought a “sex cult” was operating inside Agama, and two formal accusations of rape against Tarcau were filed, though the three-month statute of limitations on rape cases in Thailand meant they could not be investigated by Koh Phangan police.

Tarcau was also accused of using his influence to promote “dangerous” health theories, which allegedly contributed to at least two women not seeking treatment for cancer with “devastating consequences”. The school remains stripped of its Yoga Alliance certification.

Tarcau left Thailand when several of the victims went public. The school apologised for “any harm that any Agama teacher may have caused” and pledged they were “dedicated to change”, hiring a consultant to carry out an independent investigation, before closing down operations to carry out a “restructuring”.

But the Guardian can reveal that Tarcau has since returned to Koh Phangan and reopened Agama, where he is once again teaching female pupils in classes and workshops. On the Agama website in December he was listed as the teacher leading a New Year retreat as well as other yoga workshops, though later all teachers’ names were removed from the website.

Several other teachers who were also accused of misconduct, rape, assault, or were accused of being part of attempts to cover up the allegation, have also returned to teach at the school.

Multiple female complainants told the Guardian of their distress that the school had reopened with no acknowledgement of the allegations.

Agama has also been accused of covering up the results of the investigation into the alleged abuse, which was carried out by independent consultant Helen Nolan. It is understood that none of those interviewed for the report have been sent a copy and its author has been banned from discussing or publishing her findings.

Nolan told the Guardian that “despite being told that my report would be published, it was not. I was also reminded that my contract included a confidentiality clause, so I was not allowed to share the report with anyone.”

Nolan said legally she was unable to discuss the contents of her final report but added: “The fact that they didn’t publish the report is telling in itself.” However, the Guardian understands that the report was “very critical” of Agama and could open the school up to lawsuits.

Agama did not respond to multiple requests for comment. In previous statements to the Guardian, the school apologised for the “suffering expressed by many women” and added that “we have not, at any point, denied the allegations”, but also claimed there was a “campaign of hate” against the school.

As well as allegations of sexual misconduct, concerns have been raised that the same alleged “brainwashing’ and “dangerous” health theories would resume with the school’s reopening with Tarcau at its helm.

Ana Smith, the mother of former Agama pupil, Deborah Topp, claimed that in 2017 Tarcau convinced her daughter not to return to Australia for breast cancer treatment and instead follow his natural remedies, which included eating only brown rice and drinking her own urine and menstrual blood, which she said he claimed to have used in the past to “successfully cure cancer”.

According to her mother, Topp only returned to Australia months later after the lump had grown rapidly and it emerged that “the three months she had stayed at Agama had been crucial to her survival”, said Smith. Despite a mastectomy, it was “too late”, said Smith, as the cancer had spread and “her chances of survival had long expired”. Topp died in December 2017.

Smith, who said she was speaking out only because she had heard that Tarcau was reopening Agama, said she was “still trying to come to terms with this man’s arrogance and God-like image of himself”, which she claimed had contributed to her daughter’s death.

“There is only regret that I did not travel to Agama and forcefully remove her from this man’s grip and influence,” she said. Agama did not respond to these direct allegations.

After Tarcau returned to the island in late October staff member Mihaiela Pentiuc, who had promised reform in his absence, resigned.

In a message on the school’s Facebook page she wrote: “I no longer have the authority nor the support to continue the internal restructuring and changes started under my initiative.”

Since it has reopened, Agama has introduced “Boundaries and Consent/Conscious Touch Workshops”, which are mandatory for those taking part in tantra workshops, although the school has been accused of using this for profit, charging every pupil an additional fee to attend the class. Agama would not clarify if Tarcau or other accused teachers would be running these sessions.

Due to the three-month statute of limitations on rape cases in Thailand, the police were unable to carry out an investigation into the rape reports filed against Tarcau. Koh Phangan police colonel Sathit Kongniam confirmed they were “still monitoring” Agama, and made regular visits to the school, although told the Guardian the police believed that Tarcau was no longer at the school.