An ancient drug has found a new illegal market in Philadelphia.

The drug, khat, is a stimulant with varying degrees of potency. It is found in the leaf of an evergreen shrub from East Africa and the Arabian peninsula, both places where it is widely used.

Philadelphia police said yesterday they seized 740 pounds of khat wrapped in burlap and packed in 17 boxes in a house in East Falls on Wednesday.

Inspector Aaron Horne said nobody had been arrested but investigators had a "person of interest." The seizure apparently was the first of its kind in Pennsylvania.

"We've never experienced khat before," Horne said, adding that police contacted their counterparts in New York to determine what they had found.

Horne said that authorities believe the market for khat is within the city's African immigrant community but that they wanted to alert the public to the drug's existence because it is cheap and may have moved outside its traditional market.

"Unsuspecting parents might not recognize it as a drug," he said. "One tip-off is if you see your kid take a sudden interest in 'chewing tobacco.' "

The active chemicals in khat - which predates coffee - are ingested by chewing the leaf or brewing it as tea.

Abdelgabr Adam, a gastroenterologist from Sudan, said he knew khat was being consumed in Philadelphia.

"It's used here all the time, especially by those who drive cabs, those who want to stay up all night," he said.

He said that despite its acceptance in some communities, khat is still a dangerous substance. "Like any other amphetamine, it is dangerous," Adam said.

In one West Philadelphia neighborhood yesterday, a man from Burkina Faso, who asked not to be identified by name, also confirmed khat's presence in the city.

"A lot of people use it, a lot of taxi drivers," he said.

In the places where the shrub Catha edulis is grown, khat is often sold by roadsides and is widely used by truckers.

But it is banned in the United States and other countries because it contains the stimulant cathinone when it it is fresh, or cathine, when it is dry.

Cathinone is a powerful Schedule 1 narcotic under federal law, and cathine is a less potent Schedule 4 narcotic.

Horne said the seized khat was dry and qualified as a Schedule 4 narcotic.

Besides acting as a stimulant, khat can induce a sense of euphoria and sometimes psychosis, officials said.

British researchers earlier this year reported that out of 20 addictive substances, khat ranked last in harmfulness as assessed by health, crime and science professionals surveyed.

The 740-pound khat seizure has a street value of $140,000 compared with $100,000 for a kilo - or 2.2 pounds - of cocaine, said Horne.