Two thick white candles flicker on either side of the plain black condolence book in the foyer of the Dublin language school Feng Yue attended until last week.

At lunchtime yesterday students at the Dame Street Centre of English Studies gathered round to sign the book, which is to be posted to his parents in China.

The spiral-bound book left no space for personal tributes, so the students simply wrote their names and their countries of origin, including Germany, Libya, China and Spain.

The discovery of the strangled and charred corpses of Mr Feng and his girlfriend, Quing Liu, both 19, in their Dublin flat last Wednesday has had an unsettling effect on students and staff.

"It shakes people, and particularly young people who are away from home and they are a good distance away," said the centre's managing director, Ms Rosemary Quinn.

Gardai are trying to establish a motive for the double murder, but have said there is no indication it was racially motivated. The range of possible motives includes a financial debt, a grudge, a crime of passion or a professional attack by the notorious Chinese crime gangs known as triads.

Garda investigations are being hampered because it has to use translators to interview many of the friends of the couple.

Mr Feng and Ms Quing lived alone in a one-bedroom flat in a red-brick apartment complex on North King Street, Stoneybatter, north Dublin. Gardai believe in the past they may have shared the apartment with up to three other people, as is fairly typical with Chinese students. This would leave open the possibility of others having keys to the premises.

A loud bang at around 1 a.m. on Wednesday was the first thing that alerted neighbours in the three-year-old complex. As apartments were evacuated, the door of the couple's flat was forced in by residents. Mr Feng and Ms Quing were found lying on the bed, badly burned. They had both been strangled before the room was set alight with the use of petrol or some other accelerant. A neighbour is reported to have seen a man running away from the Blackhall Square complex.

Two members of the Asian community have been strangled in Dublin and Belfast in recent years. Mandy Fong (28), from Malaysia, was five months pregnant when she was found in the bathroom of a rented flat in Crumlin. A Chinese waitress, Mi Yi Ho (29), was also found beaten and strangled in her east Belfast home in June 1998. She too was pregnant, and police believed she had been having an affair with a married man. A man has been charged with her murder.

Staff at Mr Feng's college described him as a very pleasant and diligent student. He had studied at another language school for six months before enrolling for an advanced English course at the Dame Street centre.

Ms Quing was doing an intermediate-level English course at the Swan Training Institute on Grafton Street. Staff described her yesterday as a "private person" and a hard-working student who was enrolled for 20 hours' tuition a week.

Mr Oliver Lyons from the Swan Training Institute said it was planning some form of commemoration for Ms Quing, including a book of condolences. "We are checking with other students as to what's appropriate to do, given that she's from a nonreligious country," he said. Both students were from Shenyang province, an industrialised area of north-eastern China. Both had returned to Dublin in recent months after visiting home for the Chinese new year last January.

The schools Mr Feng and Ms Quing attended say up to a third of their pupils are Chinese. Many will graduate to private colleges in Ireland where courses in business, computers and accountancy are popular choices. Some return to China to work or set up their own businesses, while others remain in Ireland or Britain. Fees for English-language colleges in Dublin range from £800 for a sixweek course to £4,000 for six months, including accommodation with host families for the first eight weeks.

In some cases, the fees and travel costs may be raised through extended families. Gardai suspect that in others people borrow from money lenders for whom they then have to work to repay the money. The estimated income from non-EU third-level students studying in Ireland for the current academic year is £20 million.

THERE were 9,251 applications from Chinese people for visas last year, according to the Department of Foreign Affairs. That was a threefold increase on the previous year. The number of visas granted last year is not available, a spokeswoman said. However, the Beijing Embassy is so busy with visa applications it plans to set up a special visa unit this year.

Immigration gardai believe some young Chinese people use the student visa scheme to get to Ireland to work illegally, usually in low-paid catering or cleaning jobs. They are required to show documentary proof they are attending college for a minimum number of hours a week.

"There would be suspicions that some of those documents are not genuine," said one Garda source.

Mr Feng and Ms Quing were both registered as students in Ireland, and Ms Quing is believed to have worked part-time in a restaurant in Malahide.

Like most other Chinese students in Ireland, they led quiet lives outside college. "They generally keep to themselves and they are very very diligent and sincere and respectful," said Mr Lyons.