Difficulties breathing, abdominal pain and vomiting. These are the symptoms experienced by Ugandan women working at a flower farm who were told to cut flowers in greenhouses that had been fumigated with a toxic chemical a day before.

More than 80 Ugandan women accuse a Dutch-owned flower exporter of exposing them to a toxic fumigant, in a case that suggests the difficult conditions faced by African workers at the lowest end of the lucrative international flower industry.

The women were sickened by metam sodium, a soil fumigant widely used internationally as an agricultural pesticide, The Associated Press learned in interviews with some of the women, the leader of a trade union, lawyers and a manager at the flower exporter, Royal Van Zanten.

The women charge that known safety regulations were violated when they were ordered to work in a greenhouse just 24 hours after fumigation in mid-October. Many of the women were hospitalized and some said their jobs were threatened if they did not return to work or sought treatment at clinics not authorized by Royal Van Zanten.

"These actions amount to violence against women, cruel, inhuman and degrading treatment," said Irene Ovonji Odida, the leader of an association of female lawyers known as FIDA Uganda. "In our view, the actions of Royal Van Zanten ... violate Ugandan laws, European Union and global standards on business, investment and human rights."

At least four women were hospitalized weeks after the incident on Oct. 14, according to FIDA Uganda, which said it had collected evidence to support a possible criminal or civil case against Royal Van Zanten. Further tests are being done to establish whether the women will suffer lasting health problems, the group said.

Metam sodium is a "probable human carcinogen" that is highly toxic to mammals, birds and fish, according to the U.S. Environmental Protection Agency, which categorizes the fumigant as a "restricted use pesticide" and recommends a minimum of five working days before workers can re-enter following fumigation. It can cause birth defects and fetal death, according to Beyond Pesticides, a U.S.-based group.

Royal Van Zanten said about 45 women had been sickened by metam sodium and they had all been treated, according to Sam Wambi, the company's human resources manager in Uganda, who said he spoke for the company.

Following the allegations, Royal Van Zanten temporarily discontinued use of metam sodium and instead steams its flower beds, Wambi said. He said new precautions would be followed when the use of the pesticide resumes.

Now, flower pickers will not be required to return to greenhouses until seven days after any fumigants have been applied, he said.

"Whatever happened was an accident and we need to all sit on the round table and discuss and see how best we can assist those workers who were affected so that they are properly treated," said Rosemary Ssenabulya, the head of the Federation of Uganda Employers, of which Royal Van Zanten is a member.

Resty Nantume, one of the women hospitalized, said she knew she was in trouble when she entered a greenhouse and smelled metam sodium, which the workers knew to be toxic. When she and other colleagues started experiencing breathing difficulties, they complained to their bosses "who told us there was no problem," she said.

Workers normally do not return to greenhouses until five days after the application of metam sodium, said Jennifer Nassali, the leader of a trade union for workers in the flower industry.

Royal Van Zanten operates two chrysanthemum farms just outside Uganda's capital, Kampala, and employs more than 1,200 Ugandans, many of them young women in this East African country where per capita income was $724 in 2014.

Some of Royal Van Zanten's employees here say they work under tough conditions and can be fired if they complain about safety issues. For many, the basic pay is less than $50 a month, according to FIDA Uganda.

"This is real daylight slavery," said Eunice Musiime, the head of Akina Mama wa Afrika, a women's rights group based in Uganda.

Horticulture is big business in some African countries, providing substantial exports and tax revenue.

In neighboring Kenya, where there have been similar concerns about the safety of workers in flower farms, exports rose from 86,480 tons in 2006 to 136,601 tons in 2014, making Kenya one of the top exporters to the European Union. Flower exports earned Kenya more than $500 million last year, according to government statistics. Uganda does not have up to date statistics for the value of its flower exports, which go primarily to European markets.