The Metropolitan Police Department last week arrested executives of a Japanese engineering company, Seishin Enterprise Co., on suspicion of illegally exporting to Iran sensitive military-related equipment that could be used in the manufacture of solid fuel for missiles. Investigations have also revealed that the Tokyo-based firm sold the same type of jet mill to North Korea in 1994.

A jet mill is a machine tool that uses high-pressure air jets to crush solids into superfine powder. Ammonium perchlorate, a solid propellant for missiles, is pulverized to improve its combustion efficiency and extend the range of missiles. Experts also say solid fuel is easier to transport than liquid fuel and requires less time to inject.

There is indeed a strong possibility, as investigators suggest, that the milling equipment might have been used in the two countries' missile-development programs. Iran and North Korea allegedly have close ties in weapons-related areas, such as missile development and exports. The possibility also remains that some of the missiles and other weapons they have produced might have transferred to terrorist organizations.