Investigators from Hong Kong will travel to Indonesia to speak with a woman who left the Chinese city after she was allegedly tortured by her employer, authorities said Friday, adding they will pursue the case "relentlessly".

Erwiana Sulistyaningsih, a 22-year-old former domestic helper, was reportedly left unable to walk after eight months of alleged abuse at the hands of the employer. She was admitted to an Indonesian hospital in critical condition after returning home last week.

Domestic workers took to the streets of Hong Kong in support of Erwiana Thursday, and demanded better protection for the city's hundreds of thousands of foreign helpers.

During the protest, a second maid known only as "Bunga" also came forward to allege abuse at the hands of the same employer -- reported to be a woman in her forties who lives with two teenage sons and a husband who is often away -- four years ago.

Authorities promised action and have said police officers will be sent to Indonesia to speak with Erwiana.

"Police will be liaising with Interpol with a view to sending officers to Indonesia to take a statement from the helper," Labour and Welfare minister Matthew Cheung told a press conference on Friday.

"We do not tolerate any abuse or exploitation of domestic helpers in Hong Kong," Cheung said, adding that the government will "pursue the case relentlessly".

Cheung also said the government will step up enforcement action over regulation and inspection of domestic helper employment agencies.

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

Erwiana 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, a spokeswoman for the Indonesian minister of manpower and transmigration has said.

The employers accused of the abuse have yet to comment publicly on the case.

The allegations have renewed concerns about the treatment of domestic helpers in the southern Chinese city, home to nearly 300,000 maids mainly from Southeast Asian countries -- predominantly Indonesia and the Philippines.

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.

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