An Iranian firm closely linked to Tehran’s nuclear program acquired special hardware for enriching uranium, despite sanctions intended to keep such equipment out of Iran, according to officials with knowledge of the matter.

In recent weeks, the officials said, an Iranian procurement firm obtained critical valves and vacuum gauges made by a French company that until December was owned by U.S. industrial conglomerate Tyco International. The French and U.S. firms said they knew nothing of the case.

Western authorities are still struggling to understand precisely how the valves and gauges in question reached Iran. The International Atomic Energy Agency is investigating the matter, according to a Vienna-based diplomat, and Western intelligence agencies also are investigating, The Wall Street Journal has learned.

A Jan. 14 email that triggered the IAEA investigation alleged that the valves moved through an intermediary representing a Chinese company based near Shanghai.

Full story: Iran Nuclear Ring Probed – WSJ.com