The U.S. Navy announced Sunday it seized a boat in the Gulf of Oman carrying fertilizer used to make explosives that was caught last year smuggling weapons to Yemen. The British royal navy said it confiscated 1,041 kilograms (2,295 pounds) of illegal drugs in the same waters.

The interdictions were just the latest in the volatile waters of the Persian Gulf as American and British authorities step up seizures of contraband during the grinding conflict in Yemen and ongoing drug trafficking in the region.

The U.S. Navy’s Mideast-based 5th Fleet said its guided-missile destroyer USS Cole and patrol ships halted and searched the sailboat, a stateless fishing dhow, that was sailing from Iran on a well-worn maritime arms smuggling route to war-ravaged Yemen last Tuesday. U.S. forces found 40 tons of urea fertilizer, known to be a key ingredient in homemade improvised explosive devices, hidden on board.

Authorities said the vessel had been previously seized off the coast of Somalia and found last year to be loaded with thousands of assault rifles and rocket launchers, among other weapons. U.N. experts say weapons with such technical characteristics likely come from Iran to support the Houthi rebels. The Navy turned over the vessel, cargo and Yemeni crew to Yemen’s coast guard earlier this week.

Yemen is awash with small arms that have been smuggled into the country’s poorly controlled ports over years of conflict. Since 2015, Iranian-backed Houthi rebels have been battling a Saudi-led military coalition for control of the nation. Iran says it politically supports the rebels but denies arming them, despite evidence to the contrary.

The smuggled weapons have helped the Houthis gain an edge against the Saudi-led coalition in the seven-year war. Violence has drastically escalated over the past week amid stalled international attempts at brokering peace. Following a deadly drone attack claimed by the rebels on Abu Dhabi, in the United Arab Emirates, Saudi warplanes pounded the northern rebel-held province of Saada, hitting a prison and killing over 80 detainees.

Officials also revealed Sunday that a British royal navy vessel had seized a large quantity of illegal drugs valued at some $26 million from a boat sailing through the Gulf of Oman on Jan. 15.

The HMS Montrose confiscated 663 kilograms (1,461 pounds) of heroin, 87 kilograms (191 pounds) of methamphetamine and 291 kilograms (641 pounds) of hashish and marijuana, the joint maritime task force said in a statement.

The task force did not elaborate on where the drugs came from, who manufactured them or their ultimate destination. But Iran over the last decade has seen an explosion in the use of methamphetamine, known locally as “shisheh” or “glass” in Farsi, which has bled into neighboring countries.

(AP)