Federal authorities investigating the recent deaths of two University of Mississippi students have charged a store clerk and his son with selling an illegal kratom product. This was reported by Qazaqyia.kz citing The Guardian.

Prosecutors announced on Friday that a drug taskforce in Mississippi had previously urged people to avoid kratom, an herbal substance that acts as a stimulant at low doses and a sedative at high doses, after authorities found packages of kratom derivatives while investigating the deaths on 21 September.

It is still not clear whether those substances contributed to either death, but federal prosecutors said both appear consistent with drug overdoses. Two state agencies were working to expedite toxicology reports for the students, Mississippi governor Tate Reeves said in a 23 September statement. The Lafayette county metro narcotics unit said on Thursday that the investigation remained active and additional charges were possible.

Bank records show one of the students, Aidan Hamilton, made multiple purchases in September from a vape, tobacco and beer store in Oxford, Mississippi, where the university is located, according to a federal court filing.

On 24 September, an informant sent to the store by investigators bought kratom-based pills from the clerk, 51-year-old Yahya Mohamed Mosleh, who warned the informant to “be careful taking the pills because people were dying from them”, the US Drug Enforcement Administration (DEA) special agent Michael Dassance said in an affidavit.

Authorities later detained Mosleh and his son, 18-year-old Islam Yahya Mosleh, who was working behind the counter, and charged them each with one count of possession with the intent to distribute a controlled substance.

Attorneys Scott Davis and AE Harlow Jr, who respectively represent the elder Mosleh and Islam Mosleh, said in emails that they had no comment. The defendants appeared on Thursday before a magistrate judge, who ruled there was sufficient evidence to charge them.

Kratom, which comes from a tree native to south-east Asia, is legal at the federal level. But some state and local governments have banned it, and federal authorities have issued warnings about its risks.

Proponents say that in its pure, ground-leaf form, kratom is a safe, natural herbal supplement that can help manage pain, anxiety and depression, and ease the effects of opioid withdrawal. They say the danger is from kratom derivatives, which are often synthetic and can be highly potent.

In August, the DEA banned three kratom-related compounds.

The 25 September affidavit from Dassance, the DEA agent, said one of the banned compounds was listed as an ingredient in products seized from the Oxford store and Hamilton’s room.

Hamilton – a freshman from Englewood, Colorado – and the other student who died, Robert Strang, a junior from Atlanta, were found in different locations, one on campus and the other off campus.

Investigators found opened packages of kratom or synthetic kratom, labeled “Smax”, in Hamilton’s room with some pills missing, according to the DEA agent’s affidavit. A package of Smax was also found in Strang’s room, though the affidavit says he bought it from a different store.

Yahya Mosleh told the informant who went to the store on 24 September to be quiet when other customers came in and pushed the kratom pills out of sight. When the customers left, he completed the sale, according to the affidavit, again telling the informant to be careful.

Eleven states have banned kratom. Others, including Mississippi, have regulated it, in part by requiring people to be 21 or older to buy it.

The city of Oxford, additionally, has implemented its own kratom ban.