The Ministry of Foreign Affairs issued a statement saying the reports were being looked into by the Israeli embassy in Mexico.
According to local media, Helbrans' body was pulled from the river by rescue forces on Friday afternoon after the rabbi was swept away by strong currents while swimming before Shabbat.
Rabbi Helbrans was the head of a group of forty ultra-Orthodox families who entered the state of Chiapas about three weeks ago, after crossing the border from Guatemala.
From Israel to the US, Canada, Guatemala and finally Mexico
Helbrans was born Shlomo Elbarnes into a secular family in Jerusalem, only becoming religious as a young man. He studied at the Itri Yeshiva in Jerusalem before founding the Lev Tahor sect in the 1980s.
Lev Tahor is an ultra-Orthodox sect comprised of predominantly Israeli Haredi extremists who leave their families behind in Israel as part of a wider boycott of Zionism. The group is widely considered to be a cult for its extreme conduct which adheres to the strict word of Jewish scripture.
In the 1990s, the movement was under investigation by Israeli authorities for allegedly collaborating with Islamist elements against state security. Helbrans fled to the United States along with several students who were smuggled out of Israel with fake passports. As such, an additional investigation into Helbrans for kidnapping was launched.
Whilst in the United States, Helbrans was arrested and served two years in prison for kidnapping after assisting a 13-year-old boy go into hiding from his secular mother.
After his release from prison in the US, Helbrans was to be deported to Israel, but instead fled to Canada where he was granted refugee status after claiming persecution in Israel for his religious and political beliefs.
Underage marriage, beatings and psychiatric drugs
According to estimates, the sect numbers about 230 people, of whom about 150 are children.
About three and a half years ago, Canadian authorities blocked the group from transferring underage members to Guatemala after Canadian courts issued a decree requiring some children to be transferred to foster families after being found to have been severely abused.
Welfare officials in Ontario and Quebec claimed that they had evidence of abuse involving beatings, underage marriage, and illegal education. However, the sect succeeded in transferring a number of the children to Guatemala giving rise to a legal battle over the last few years to expel them back to Canada.
In September 2016, at the request of Israeli authorities, Guatemalan law enforcement raided the Lev Tahor compound and arrested its leaders on suspicion of child abuse. The raid prompted its members to leave the site to a new location in eastern Guatemala, and complain that they were being persecuted due of their faith.
Helbrans and the group had crossed the Guatemalan border into the Mexican state of Chiapas several weeks ago.