What is kratom, the 'gas station heroin' alarming officials in the US?
Kratom, found during an investigation into the deaths of two college students, has been sold in the US for around a decade.
What is kratom, the 'gas station heroin' alarming officials in the US?
Jeffrey Deaver, a 58-year-old retired timber cutter in Washington state, has been using kratom for four years to ease severe chronic pain in his hips and knees.
He came across the herbal product after doctors could not relieve his pain and while he was waiting for surgeries. At first he was afraid, so he "started small", but he gradually took more until the pain disappeared.
"It was like a miracle," Deaver said. "I could sleep. I could function.
"I just don't know what I'd do without it."
Kratom - an herb with opioid-like effects - has become increasingly popular in the US over the past decade, and is usually bought over the counter and taken in pill or liquid form.
This week, investigators found packaged kratom among the belongings of two University of Mississippi students who died. Their deaths were not blamed on kratom, but officials are now warning about its use.
For years, anti-kratom campaigners have called for bans, and in some countries, such as the UK, it is illegal. But kratom is not regulated by the US Food and Drug Administration and remains legal in some states, including Mississippi.
Kratom is a tree native to Southeast Asia, in countries including Thailand, Malaysia and Indonesia.
It has been used for centuries for its stimulant effects, ground up and consumed much like tea.
As its popularity spread worldwide, it entered the US market as a supplement around 2016.
"That's really where the problems began," said Dr Shane Speights, dean of the New York Institute of Technology College of Osteopathic Medicine at Arkansas State University.
In the US, kratom is mostly sold in highly concentrated forms, either as pills, powder or liquid, Speights said.
It is also widely available, sold everywhere from convenience stores and petrol stations to vape shops.
And because it is classified as a supplement, kratom products are not federally regulated.
"There's no way to know exactly what you're getting," Speight said. "You could go and create something in your basement, market it as a supplement, and nobody's really going to check and see what's in it."
Kratom is often promoted as a safe, natural herbal supplement for pain management, anxiety and depression.
At lower doses, its stimulant properties produce a "caffeine-kind of buzz", Speights explained.
Because of its opioid-like effects, it has also been used in an effort to curb addictions to real opioids such as fentanyl.
Those effects come from the way the plant's compounds - such as 7-Hydroxymitragynine - activate different hormones, including dopamine.
"It's almost like taking a narcotic," Speights said. "At higher doses, it can create more euphoria and give you more of a general high."
Hallucinations are also possible.
Higher doses also bring a greater risk of harmful side effects.
That includes central nervous system (CNS) depression - which is "where the deaths come in," Speights said.
CNS can lead to cardiovascular collapse and loss of breathing.
Withdrawal symptoms and addiction are also risks, said Jana Wu, director of clinical integration at the addiction treatment centre Mountainside.
"It affects marriages, relationships," she said. "I've seen people lose jobs, spend thousands of dollars a month on it."
Because it is easy to build up a high tolerance to the herb, users may need to take more and more over time to get the same effect.
"I've worked with people that were taking like up to 20 pills a day," Wu said.
Experts told the BBC that the biggest danger is that kratom is not federally regulated.
"Is there a safe dose?" Speights said. "My answer is going to be no because - I'm going to go back to this - we don't know what's in it."
Kratom is banned in 11 states: Alabama, Arkansas, Connecticut, Indiana, Kansas, Louisiana, Massachusetts, North Dakota, Tennessee, Vermont and Wisconsin.
Massachusetts was the most recent state to outlaw it, issuing a temporary emergency order in August.
Ten years earlier, the US Drug Enforcement Agency (DEA) had tried to classify kratom as a Schedule 1 drug, the most dangerous category, calling it "an imminent hazard to public safety".
But the effort failed a few months later, after the justice department said it had received "numerous comments from members of the public challenging" the attempt.
That leaves states to act, such as Arizona, which recently sued a company selling kratom beverage products.
Groups opposed to kratom want states to do more, saying "gas-station drugs are poisoning our communities".
Pro-kratom groups like the American Kratom Association are pushing for bans on synthetics "posing as natural kratom".
Internationally, kratom is banned in the UK. In Europe, the laws vary by country.
In Malaysia, where the kratom tree is native, consumption and sale are banned under the Poisons Act of 1952.