A top investigator said the four suspects included Onel de Guzman, a computer school dropout who has said he may have released the virus by accident.

The bug caused up to $10bn damage

The Love Bug crippled computers worldwide causing billions of dollars of damage when it was released on 4 May.

Investigators believe the virus emanated from a computer in a flat in Manila, where Mr de Guzman lives with his sister Irene.

Accident

At a press conference on Thursday, Mr de Guzman told reporters he may have released the virus by mistake
.

De Guzman dropped out of school

He did not directly say whether he had written the Love Bug. But asked if he might have released it into cyberspace, he replied: "It is possible".

The virus, which spread via an e-mail bearing the line "ILOVEYOU", affected tens of millions of computers, including ones at the Pentagon and the UK Parliament.

Earlier this year, Mr de Guzman, a former student at Manila's AMA Computer College, wrote a thesis project describing an e-mail stealing programme similar to the Love Bug.

He failed to graduate after the school rejected his paper as unethical, saying it did not condone "burglary".

Arrest

Carlos Caabay, deputy director of the National Bureau of Investigation (NBI), said they were looking into Mr de Guzman's statement.

Carlos Caabay: No arrest warrants

But he said no arrest warrant had been issued because the investigation was still under way.

The only person arrested so far is Ms de Guzman's live-in boyfriend Reonel Ramones.

He is expected to be charged on 19 May under the Access Device Act which covers illegal use of passwords.

Suspects

Investigators said the names of the suspects had appeared on diskettes which were seized on Monday from the de Guzman's flat, where Mr Ramones was arrested.

Technicians say they have discovered encrypted messages containing 10 encoded names.

But some of these could be pseudonyms for the same person.

The names have been traced back to AMA Computer College (AMACC).

Thesis

AMACC said Mr de Guzman had excelled in his computer courses, but dropped out after his thesis proposal was rejected.

Tackling the virus

Do not open it Delete it using shift del As with all e-mails, if in doubt do not run any attachments you are not expecting If you have run the attachment, isolate your machine from any network and phone your help desk or seek expert advice Remember to keep your anti-virus software up-to-date and be vigilant about attachments

In his paper, Mr de Guzman said his software would help people obtain Windows passwords and spend more time on the internet without paying.

He wrote that users would be able to "steal and retrieve internet accounts of the victim's computer".

Reports say officials from AMACC are also focusing attention on another student, Michael Buen, a close friend of Mr de Guzman's.

Both are said to be members of an underground computer group that wrote and sold thesis projects to other students.

The Love Bug virus destroys user files, steals passwords and replicates itself through the user's address book.

It only affects systems running Microsoft Windows with Windows Scripting Host enabled. Computers using Apple's operating system or Linux are not affected.