NEOSHO, Mo. — The hospitalization of three Neosho teenagers has led to the seizure of a large amount of synthetic marijuana from a Neosho convenience store, authorities said Friday at a press conference.

Newton County Sheriff Ken Copeland said that at about 4:15 p.m. Thursday an officer observed three teenage males in the 200 block of East Spring Street. Two of the teens were unconscious and the third was convulsing in the street, he said.

He said authorities determined that the boys were under the influence of synthetic marijuana — known as “syn” — and that the substance was allegedly purchased at a local convenience store.

Neosho police Chief Dave McCracken said the teens were hospitalized and kept overnight for observation, but were expected to be released Friday.

Copeland said authorities obtained a search warrant for the store, and officers and deputies executed the warrant at about 5:30 p.m. Thursday.

Copeland said they seized a large amount of synthetic marijuana with a retail value estimated at about $71,000. He said a field test was conducted on a sample from the store, and it tested positive for controlled substances that are banned under state law.

Copeland said more samples are being sent to a crime lab, and if they are found to contain controlled substances, charges will be filed against the store’s owner.

Newton County Prosecutor Jacob Skouby said the charges of possession of a controlled substance with intent to distribute, or distribution of a controlled substance could be filed. He said both offenses carry a punishment range of five to 15 years in prison.

McCracken said the teens told officers that a stepfather of one of the boys purchased the substance for them. McCracken said a case is being prepared and charges could be filed against the stepfather as well.

FAIR WARNING

Copeland said his department conducted an undercover operation this spring to determine which stores in the county were selling synthetic marijuana.

He said that although the substance is sold as potpourri or incense, several store clerks instructed undercover officers that the product was meant to be smoked.

Following the undercover sweep, Skouby sent a letter to business owners who were selling the substance.

The letter, dated May 16, told store owners: “The purpose of this letter is not to appeal to your moral character or to call upon your sense of community, it is to warn you of the legal troubles you face.”

The letter warned that much of the synthetic marijuana purchased by law enforcement still contains banned substances and that manufacturers’ lab reports indicating otherwise were often forgeries.

Skouby warned store owners that if they did not “remove this product from your shelves immediately and permanently,” they would be prosecuted “to the fullest extent possible.”

Skouby also said that rather than focusing his prosecution on the clerks who made the sale, “I will focus the prosecution on you the owner of the store.”

Globe calls to the convenience store searched went unanswered Friday.

INCENSE OR SYN?

Skouby said if lab results determine the confiscated “syn” contains banned substances, the next step is to prosecute the store owner. He said it would be up to a jury to decide whether he was knowingly selling a controlled substance, but that the selling price of the substance is far beyond what is normally paid for incense.

“When you’re selling it for $10 a gram, it raises the issue in the average juror’s mind that you know it’s not incense or potpourri, you know what people are doing with it,” Skouby said. “It would be risky to end up in front of a jury and try to convince them that you didn’t know that what you were selling was a controlled substance.”

Skouby also said store owners put age restrictions on the purchase of the substance, which he sees as an acknowledgment that it is not just incense.

“They’re not selling it to kids because they know it’s being misused,” he said. “They think they’re being responsible, but it’s really an admission that they know it’s being misused. If it’s really potpourri, there’s no reason a 13-year-old shouldn’t be able to buy it. I think there’s a perverse admission there that if they thought about it they’d have to acknowledge.”

Andy Pike, a drug detective with the Newton County Sheriff’s Department, said store owners are attracted by the potential profits selling synthetic marijuana can bring. He said that in the course of the department’s undercover investigation they saw packets of “syn” selling for as much as $70.

“I think the store owners know exactly what it is used for, but on the other hand, the money is so good they’re looking at the dollars and cents,” he said.

CHANGING THE RECIPE

Pike said the manufacture of synthetic marijuana is not regulated by any government agency because it is supposedly not intended for human consumption. He said because there is no oversight, the potency of the product can vary greatly.

“It’s a chemical that they spray on the herbs or spices,” he said. “They spray it on with a garden sprayer in garages or basements, or manufacturing plants, but the process is not controlled. Some portions may be sprayed heavier than others.”

McCracken said the varying intensity has already had fatal results. He said two fatalities in Neosho have been linked to synthetic marijuana.

McCracken said that his department has seen roughly a dozen juveniles hospitalized in the past year because of health problems resulting from smoking synthetic marijuana.

“During the period after school was out, there were several incidents where kids were taken to the hospital suffering from seizure type events or respiratory distress,” he said. “Unconsciousness is also a symptom.”

McCracken said he knows of three stores in Neosho that are still selling synthetic marijuana. He said that is three too many.

“I’m not going to rest until this stuff is out of the community,” he said. “They are aware that this is hurting our community and hurting our children, and we don’t plan to sit idly by while they play their games with the formula.”