A CHEWABLE African shrub used by Somali gunmen fighting US troops in Mogadishu is posing concerns for US East Coast federal officials who believe it may offer the latest cheap amphetamine high. Khat — also known as “qat” — is traditionally used as a mild stimulant in African and some Middle Eastern countries. But US Customs Service officials believe the drug, which is more potent soon after harvest, has started to make inroads into the illegal stimulant market in New York and New Jersey. “It used to be an ethnic thing, but it’s spread and now we have college kids using it, ” said government spokesman Thomas Manifase at the US Customs’ New Jersey office. The Customs Service reports that at New Jersey’s Newark Airport, agents have uncovered five tonnes of khat — about 2.1 million dollars worth — since October and another 11 tonnes at John F. Kennedy Airport.