WASHINGTON — The U.S. military is questioning an Islamic State militant who allegedly has helped lead the extremist group's nascent effort to acquire and use illicit chemical weapons in Iraq and Syria, U.S. officials said Wednesday.

Officials said the operative is believed to have worked for Iraqi leader Saddam Hussein's unconventional weapons program, which produced vast stockpiles of chemical and biological warfare agents prior to the 1991 Gulf War.

The operative, identified as Sulayman Dawud al-Bakkar, was captured during a U.S. special operations raid about a month ago near Tal Afar in northern Iraq, officials said.

He is in U.S. custody in Irbil, the capital of Iraq's Kurdish region.

Al-Bakkar is expected to be transferred to Iraqi custody when the interrogations are finished. But his capture has revived questions about who should hold militants taken on the battlefield.

The Pentagon, which was scarred by scandals over some of the prisons it ran during the Iraq War, has no desire to open another for this conflict. The Obama administration is seeking to empty the detention camp at Guantanamo Bay, not to make it larger.

Gen. Joseph Votel, commander of U.S. Special Operations Command, told the Senate Armed Services Committee on Tuesday that “there is a requirement for long-term detention,” but he offered no solution.

During questioning, al-Bakkar has provided details about the Islamic State's chemical weapons program, including locations of two storage sites that were later targeted in U.S. airstrikes, said the officials, who spoke on condition of anonymity. The most recent airstrike was Saturday near Mosul.

Little is publicly known about the Islamic State's access to unconventional weapons. It's not clear if they are producing poisons in laboratories or simply recycling toxic materials recovered from the pre-1991 period.

Iraq's defense minister, Khalid al-Obeidi, played down fears of gas attacks, telling reporters Wednesday in Tikrit that the Islamic State lacks “chemical capabilities.” He said chemical attacks so far sought to “hurt the morale of our fighters” and did not cause any casualties.

Navy Capt. Jeff Davis, a Pentagon spokesman, suggested a more serious threat.

He said that the Islamic State has put sulfur mustard powder into artillery shells and rockets that have been used in 12 incidents in Iraq and Syria.

“This is a group that does not observe international laws or international norms,” Davis said. “They have demonstrated that they will stop at nothing to inflict death and destruction on innocent people. As disturbing as the use of chemical weapons is, it should not come as a surprise to us that they would stoop to that.”

Kurdish authorities in northern Iraq said Islamic State militants fired mortar shells that produced “white smoke and a black liquid” on Aug. 13 in Makhmour. Some Kurdish fighters suffered breathing problems and skin injuries, the officials said, and blood tests reportedly indicated sulfur mustard.

The Organization for the Prohibition of Chemical Weapons, an intergovernmental group based in The Hague, Netherlands, reported that Islamic State fighters also used sulfur mustard a week later in an attack on Marea in northern Syria.

Mustard gas, a blister agent that burns skin, eyes and other soft tissue, was first used to devastating effect in World War I. Its use in war has been banned under international law since 1925.

After the 1991 Gulf War, United Nations weapons inspectors recovered large stockpiles of sulfur mustard, as well as nerve agents, at multiple sites in Iraq.

Some were destroyed, but many mustard-filled shells were considered too unstable to move and were sealed in concrete bunkers for safety. Some of the bunkers were left intact after the 2003 U.S.-led invasion.

The militants may have opened the bunkers after they captured large parts of western and northern Iraq in 2014 and may now be trying to repurpose the materials.

It's also possible the poison was obtained in Syria, where embattled President Bashar Assad's government produced mustard, sarin and other chemical warfare agents.

Under threat of a U.S. air attack in 2013, Assad agreed to dismantle the program and supplies were shipped out of the country and destroyed at sea. However, his forces were accused of dropping chlorine-filled barrel bombs on insurgent strongholds last year.

U.S. special operations forces grabbed the alleged Iraqi chemical weapons specialist as they began a series of late-night raids that seek to gather intelligence and kill or capture militants, officials said.

It wasn't immediately clear if he was specifically targeted or if U.S. authorities discovered his role after his capture.

The raids are carried about by a so-called expeditionary targeting force, which has about 200 commandos and is the first major U.S. combat force on the ground in Iraq since the U.S. military withdrawal in 2011.

Following a strategy developed in Iraq and Afghanistan, the U.S. teams target homes and compounds, set up safe houses and work with Iraqi and Kurdish forces to build informant networks.

They typically haul away laptops, cellphones and other electronic devices that could supply useful intelligence.

“Sometimes they'll carry out these missions multiple times a night,” one official said. “There's a domino effect. One raid might glean information that leads to another.”

The decision to deploy the commando force in Iraq came after a Delta Force raid in eastern Syria last May provided a significant trove of intelligence.

whennigan@tribpub.com