Another violent attack by a teenager in the same county as Florida's "cannibal killings" has been linked to a mysterious new type of dangerous bath salts, according to police.

The latest assault did not involve fatalities like the double murder by accused killer Austin Harrouff whom police said chewed the face and torso of one of the victims although there were striking similarities.

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In the latest case, another 19-year-old suddenly "cannon balled" through the bedroom window of a stranger's house, smashing it, and attacked two people sleeping in their beds.

The man in the house "could not get him under control," even though he outweighed the attacker by 100 pounds (45kg) Martin County Sheriff Bill Snyder said, adding: "They fought from one end of the house to the other."

The woman living in the house hit the intruder several times with a baseball bat to no effect, Snyder added.

Officers who arrived at the scene were finally able to subdue and arrest him. Similar to the Harrouff attack, the latest incident was an inexplicable assault by someone exhibiting the same "extreme strength and a high tolerance to pain," Snyder said.

Just like Harrouff after the earlier attack, the latest suspect lost consciousness after he was arrested, and had to be hospitalised and intubated, which is usually done to assist breathing.

The attacker told deputies he was high on flakka. But a friend who was with him said they had both taken LSD and a bath salt called methylone. Both bath salts and flakka have been linked to horrific hallucinations, super-human strength and even cannibalism.

Methylone is a relatively new form of highly dangerous bath salts which failed to show up in the database of the narcotics analyzer used by investigators, Snyder told the Palm Beach Post.

"We have a designer drug that we have never encountered and it is not stored in the software library of the testing equipment. We don't know what we are working with. We do know it is undoubtedly a bath salt," he said.

Euphoric high

Methylone, which has been sold as a room odorizer, is supposed to give a user a euphoric high similar to Ecstasy. It is possible that both Harrouff and the teenager were affected by the drug, and the attacks could be a sign of its increased use in the area.

Police have all the illicit substances carried by latest attack and his friends, and they are being tested. Harrouff has tested negative for several street drugs such as methamphetamine, heroin and marijuana. Results for bath salts and flakka are still pending.

Harrouff remains in hospital. He has regained consciousness for brief periods but has not yet been able to provide a statement. The sheriff's office is awaiting drug test results from the FBI lab in Quantico, Virginia.

Harrouff's father doesn't believe he was on drugs, but thinks he suffered some kind of "psychotic break" before he allegedly attacked and killed a couple sitting in their garage in Tequesta, Florida.