(Beirut) – Airstrikes by the Saudi Arabia-led coalition that hit a dairy factory in Yemen on March 31, 2015, killed at least 31 civilians and wounded another 11. The governments that participated in the attacks should investigate the airstrikes, which may have been indiscriminate or disproportionate, in violation of the laws of war.

Forces of Ansar Allah, known as the Houthis, and other opposition forces, also appeared to put civilians at unnecessary risk. Area residents told Human Rights Watch that the Yemany Dairy and Beverage factory, a multi-building compound 7 kilometers outside the Red Sea port of Hodaida, was about 100 meters from a military air base controlled by Houthi forces. Military units loyal to former President Ali Abdullah Saleh were at another nearby military camp.

“The coalition's repeated airstrikes on a dairy factory show cruel disregard for civilians, as does the deployment near the factory by Houthi and pro-Saleh forces," said Joe Stork, deputy Middle East and North Africa director. “The attack may have violated the laws of war, so the countries involved should investigate and take appropriate action, including compensating victims of unlawful strikes.”

While civilian casualties do not necessarily mean that the laws of war were violated, the high loss of civilian life in a factory seemingly used for civilian purposes should be impartially investigated, Human Rights Watch said. If the United States provided intelligence or other direct support for the airstrikes, it would as a party to the conflict share the obligation to minimize civilian harm and investigate alleged violations.

Starting at about 11:10 p.m. on March 31, one or more warplanes carried out four separate strikes that hit the dairy factory, three factory workers and three local residents told Human Rights Watch. Dr. Hani Mahfoodh, an emergency doctor at 22 May Hospital in Hodaida, which received most of the victims, told Human Rights Watch that the strikes killed at least 31 factory employees, for whom he provided the names, and wounded at least 11 more. The sources said that the dairy factory produced products for the general public, though it is not possible to rule out that Houthi or other forces also benefitted from them.

Riyadh Yassin, the foreign minister in the government of ousted President Abdu Rabu Mansour Hadi, publicly asserted that Houthi forces had shelled the factory, but provided no information to substantiate his claim.

Two people who were about 100 to 200 meters from the factory, and another who was about 2 kilometers away, said they saw one or more planes take part in the attack. A factory worker told Human Rights Watch that after his shift ended at 11 p.m., he waited with colleagues at the factory gate for the employee bus. At 11:10 p.m., he heard the sound of aircraft, which he had seen bombing elsewhere in Hodaida earlier that evening. A few seconds later, he saw one of the factory warehouses explode. “We rushed to the doors of the nearest building full of staff, and held open the doors as people ran out,” he said.

A few minutes later he saw a second explosion in a part of the factory that housed packaging equipment, causing water boilers to explode. The ground shook beneath him, he said. He later discovered that the explosion also caused leaks in gas pipes used in the cooling process. The worker said he witnessed ambulance workers take several people who may have inhaled the gas fumes to a hospital.

He said that a few minutes later he saw a third explosion in another part of the factory, setting the building on fire. Three workers in the building died while trying to turn off the machines. There was a fourth explosion several minutes later in the same part of the factory.

Another factory worker said he was inside another factory building during the first explosion. He was wounded by the second explosion but remained to aid other wounded and the ambulance staff. “In the aftermath of the strikes I saw body parts and charred bodies and hands and legs scattered,” he told Human Rights Watch. “I could not sleep for two days afterward because of the terrible images in my mind.”

A third factory employee who saw the explosions said that fires continued to blaze until the next morning.

Coalition warplanes subsequently attacked both the military air base and the neighboring military camp, on April 11.

Under the laws of war applicable to the armed conflict in Yemen, civilians and civilian objects may never be deliberate targets of attack. Attacks that fail to discriminate between civilians and combatants or that cause civilian harm disproportionate to the expected military gain of an attack are prohibited. Warring parties must take all feasible precautions to minimize harm to civilians. They should avoid deploying in densely populated civilian areas or remove civilians from the vicinity of their deployments. Governments are obliged to investigate credible allegations of violations.

The Saudi-led coalition, which includes Bahrain, Egypt, Jordan, Kuwait, Morocco, Qatar, Sudan, and United Arab Emirates, has launched airstrikes on a near-daily basis starting on March 26 against the Houthis, who effectively ousted Hadi’s government in January. Airstrikes have struck targets in densely populated areas in the capital, Sanaa, and other cities, including Saada, Hodaida, Taiz, Ibb, Lahj, al-Dale`a, Shabwa, Marib, and Aden. Airstrikes on March 30 hit a displaced persons’ camp in northern Yemen, killing at least 29 civilians. Houthi ground forces have engaged in military operations around Aden and other areas. Security concerns and travel difficulties have prevented Human Rights Watch from investigating other attacks.

As of April 14, the fighting has killed at least 364 civilians, including at least 84 children, according to the United Nations Office of the High Commissioner for Human Rights.

The US is not a member of the coalition but it has announced that it is providing logistics and intelligence support. Providing direct support to military operations would make the US a party to the armed conflict, and bound to apply the laws of war. On April 12, the Wall Street Journal reported that unnamed US officials said that the US was providing Saudi Arabia with direct targeting support for airstrikes.

“If the US is providing targeting intelligence it is a party to the conflict and is obligated to abide by the laws of war,” Stork said. “Even if not, in backing the coalition the US will want to ensure that all airstrikes and other operations are carried out in a way that avoids civilian loss of life and property, which have already reached alarming levels.”