An Australian magistrate has given authorities an additional four days to question a suspect in last week's failed car-bomb attacks in London and Glasgow.

The court decision was made as a British anti-terrorism officer arrived in Brisbane to join his Australian counterparts in the investigation. Australian police detained 27-year-old Mohamed Haneef Monday under emergency terrorism laws used for the first time. The laws allow detention without charge.

Haneef is one of eight suspects who are all doctors or worked for Britain's national health service. He is the only one held outside Britain.

Meanwhile, British police are refusing comment on news reports that the two doctors who drove a blazing vehicle into Glasgow's airport Saturday left a suicide note.

In another development, officials say a rush-hour derailment on the London subway system was not terror-related.

The incident left 37 people injured, with 11 receiving hospital treatment for minor injuries.

Wednesday, Britain lowered its national-security level from "critical" to "severe," as authorities no longer believe a terrorist attack is imminent.

Some information for this report was provided by AFP and Reuters.