The figures show that seizures of controlled drugs rose by 15 percent in 1990, a slower rate of increase than in the 2 previous years. Marijuana was involved in 90 percent of seizures. In terms of Class A drugs, the number of LSD seizures almost doubled to 2,000; while the number of heroin and cocaine seizures fell, and the total quantities increased. In terms of Class B drugs, the number of amphetamine seizures rose by 40 percent, and the quantity almost tripled. The number of drug offenders increased by 15 percent over the previous year; the number of offenders under age 21 increased by 35 percent. The use of cautioning by police continued to increase and, for the first time, more offenders were cautioned than fined. Less than 10 percent of offenders were sentenced to immediate custody.