Thurston County investigators are now questioning whether a stimulant drug often marketed as "bath salts" is linked to a double murder-suicide that left a couple and their son dead.

The state Board of Pharmacy enacted an emergency rule banning "bath salts" last Friday following a report by the state Poison Center indicating a rise in the number of people ingesting the synthetic drugs.

"Bath salts" are crystalized chemicals that are snorted, swallowed or smoked. They contain two powerful stimulants which mimic the effects of cocaine, LSD and methamphetamine. Incidents of poisonings via these substances are on the rise, hospital officials say.

Now investigators suspect the drug may explain the deaths of David Stewart, an Army sergeant, his 5-year-old son Jordan Stewart, and the boy's mother, Kristy Sampels, earlier this month.

Police say David Stewart raced past a trooper on Interstate 5, refused to pull over, shot his wife, then shot himself. His son was found dead in the couple's Spanaway home with a bag over his head and bruises on his body.

"We're going to test the husband and wife to see if it ('bath salts') was in either one of their systems, and hopefully that will paint a picture of what happened," said Thurston County Coroner Gary Warnock.

Warnock said bath salts were found "on his (David Stewart's) person -- in one of his pockets, inside the interior of the car and ... spilled out onto the roadway. It was found inside the house as well."

Investigators were initially fooled by the drug's label, indicating it was "bath salts."

"We didn't have a clue. There is a lack of education about these bath salts," said Warnock.

A recent KOMO News investigation revealed that manufacturers take advantage of a loophole in the law, combining legal chemicals to make the drug, then labelling it not for human consumption. That distinction lets them bypass rigorous federal standards.

"They do say right on the label, 'This is not for human consumption,' yet everybody trying these things knows what's going on," said Jim Williams of Washington Poison Center.

Until last week, anybody -- even kids -- could buy the drugs over the counter. With undercover cameras, KOMO staffers bought the designer drugs, no questions asked, no ID required. They were found in Seattle-area smoke shops, head shops, even mini-marts.

The state announced an emergency ban on the substances last Friday, but KOMO still found them on store shelves on Thursday.

"They know what it was manufactured for. It's all about the dollar. People are making money with this and unfortunately, people are paying with their lives by using it," said Warnock.

The Thurston County coroner said the drugs are so new, his office had never tested for them. They've sent samples off to a national lab for analysis. They're not sure how long it will take to determine if David Stewart and his wife ingested the substance.