The number of people who died when they were trapped by storm-waters surging into an illegal basement factory in Morocco rose to 28 Tuesday, officials and activists said.

Heavy rains on Monday flooded the underground textile workshop in the northern port city of Tangiers as people worked.

Authorities in Tangiers told AFP that 28 bodies -- mostly women -- had been pulled out the basement of factory, in a private property in a residential area.

"Waters... submerged the confined space," Abderrahim Kabajj, senior civil protection official told Morocco's 2M television station, which also reported 28 dead. "The victims were trapped with no way to get out."

Rights groups, the Northern Observatory for Human Rights and the Moroccan Association for Human Rights, also confirmed the toll.

The deaths have caused an outcry in the North African country.

A inquiry has been launched into the cause of the accident and those responsible.

Morocco's informal sector plays a key role in the economy, with over half of the country's textile and leather production coming from unregulated operations, according to Morocco's employers' association.

Many fail to meet official safety standards, it says.

The country has experienced heavy rains in recent weeks, after a long period of drought.

In early January, rain storms caused several dilapidated buildings to collapse in Casablanca, the country's economic capital, causing at least four deaths, according to local media. 

Poorly maintained drainage systems often exacerbate flooding in Moroccan cities.

Morocco registers some 2,000 deaths each year due to work-related accidents, "one of the highest figures" in the Middle East and North Africa, according to the Economic, Social and Environmental Council (CESE).