THE number of overseas domestic helpers working in Hong Kong rose by 4,000 during the first three months of this year. The increase brings the total number of overseas maids here to a staggering 125,000, with the Immigration Department estimating that a further three or four thousand are staying illegally. The head of the investigation section dealing with domestic helpers, Chief Investigator Huen Shu-sum, said he was extremely concerned by the number of maids overstaying their visas. ''Because of the growth in the population there are more and more cases of domestic helpers breaching their conditions of stay, by, for example, working for non-contracted employers, or simply by overstaying their visas,'' he said. Sixteen investigation officers, divided into four teams, conduct spot checks on factories, cleaning companies and restaurants to search for domestic helpers working illegally. They act on tip-offs and referrals from other sections of the Immigration Department, but Mr Huen admits the team lacks the resources to tackle the problem effectively. ''Of course we need more resources. Last year we asked for 100 extra men to tackle the overall problem of illegal workers in Hong Kong. The Government has given us less than half.'' The 46-member taskforce approved by the Legislative Council last year should become effective within the next few months, but it has yet to be decided exactly how it will be deployed. This time last year there were 121,000 foreign domestic helpers in Hong Kong, the vast majority coming from the Philippines. However, the biggest jump has been seen among Indonesian nationals. The number has almost doubled from 4,100 at the end of March last year to 7,200 this year. Pastor Charles Mcknelly, who runs a refuge and help service for domestic workers, is concerned that the rapid increase in the number of domestic helpers in the territory will enable employers to become more choosy about whom they employ to be their maid. ''What these people are doing if they don't like their maid is to just sack her, after maybe only a month. And they don't even have to give a reason for it,'' he said. More than 200 Filipino maids spent their day off yesterday scrubbing the pedestrian subway running between Star Ferry and Chater Road. Starting at 8.30 am the Filipinas from the Zoe Christian Fellowship painstakingly scraped away at stains and then mopped the subway clean. The clean-up was part of the Keep Hong Kong Clean funding scheme, run by the Urban Council. ''As a part of the local community we think it's our responsibility to help keep the subway clean,'' said Pastor Bonnie Argue, who organised the day's mop-up operation.