Domestic workers took to the streets of Hong Kong Thursday to demand justice for an Indonesian maid allegedly tortured by her employers and better protection for the city's hundreds of thousands of foreign maids.

During the protest a second maid came forward alleging abuse at the hands of the same employers four years ago.

The allegations have renewed concern about the treatment of domestic helpers in the former British colony following a spate of similar abuse cases and recent criticism by rights groups.

The first alleged victim, Erwiana Sulistyaningsih, 22, was reportedly left unable to walk following eight months of abuse in the southern Chinese city and was admitted to an Indonesian hospital in a critical condition last week after returning home.

Hong Kong police said Tuesday they had launched a criminal investigation after migrant worker groups expressed anger at earlier reports that authorities were not pursuing the case. A police spokeswoman said on Thursday the investigation was ongoing and no one had been arrested.

Dozens of protesters including maids, rights activists and migrant group members rallied outside the office of the maid's employment agency Thursday before marching on the city's Indonesian consulate.

As they marched through the bustling shopping district of Causeway Bay they chanted slogans including "We are workers. We are not slaves. Justice for Erwiana".

At the protest, a woman nicknamed "Bunga" claimed she had been abused by the same employer over the course of 10 months in 2010.

"I was beaten many times. I worked 20 hours a day," the woman, who refused to reveal her true identity, said.

"It's my first time [job] in Hong Kong. I didn't know anything. I was scared. My boss also told me not to speak out," the 28-year-old said.

The agency that employed Sulistyaningsih said they were unaware of her injuries until they were notified by their corresponding agency in Indonesia.

"There is nothing for us to clarify. It's the first time there has been a case of this kind in the 10 years we have been around [in this business]," a staff member of Chan's Asia Recruitment Centre, was quoted by Hong Kong-based Cable TV as saying Thursday.

But migrant worker groups have demanded action.

"We are very angry. So many cases have happened to Indonesian migrant workers in Hong Kong," Sring Atin, vice chairperson of Indonesian Migrant Workers Union, told reporters.

The building where the employment agency's office is located appeared to have tightened security with its grille lowered and security guards refusing to allow protesters to go upstairs.

"It is not only an issue of her being an Indonesian, but her (Sulistyaningsih) being a migrant worker and a human being," Eman Villanueva of the Filipino Migrant Workers' Union of Hong Kong, told AFP.

"We from the Philippines are also migrant workers. We know the feeling, being away from home and suffering," Villanueva added.

He called on the Hong Kong government to improve legal protection for maids, and to allow them to choose their own accommodation instead of being required to live with their employers.

Sulistyaningsih remains in hospital in Sragen, on the main Indonesian island of Java.

Her condition is improving and medics hope her injuries will be healed in two weeks, Dita Indah Sari, spokeswoman for the Indonesian minister of manpower and transmigration, told AFP Wednesday.

Sam Aryadi, vice consul for public affairs for the Indonesian Consulate General of Hong Kong, told AFP on Thursday that initial examinations on the maid showed "external injuries" on her face and her feet. "They were rather bad injuries," he said.

"We the Indonesian government will gather all the information so that we can build a case against the employer," he said, adding that evidence collected would be passed on to Hong Kong police.

The injured maids' employers have yet to comment publicly on the case.

The semi-autonomous Chinese city is home to nearly 300,000 maids from mainly Southeast Asian countries -- predominantly Indonesia and the Philippines -- and criticism from rights groups over their treatment is growing.

A Hong Kong couple were jailed in September for attacks on their Indonesian domestic helper, which included burning her with an iron and beatings with a bike chain.

Amnesty International in November condemned the "slavery-like" conditions faced by thousands of Indonesian women who work in the Asian financial hub as domestic staff and accused authorities of "inexcusable" inaction.

It found that Indonesians were exploited by recruitment and placement agencies who seize their documents and charge them excessive fees, with false promises of high salaries and good working conditions.

Maids in Hong Kong are paid about HK$4,000 ($515) a month.