Reid allegedly told investigators he had acted alone

The five were picked up on the orders of a leading French anti-terrorist judge, Jean-Louis Bruguiere.

The suspects are thought to have fed and housed Mr Reid before his alleged suicide bombing attempt on a Paris-to-Miami flight last December.

One of those held was later released.

The other four can be legally held for up to 96 hours before arraignment before a judge.

In previous investigations, Judge Bruguiere has detained minor players for questioning in the hope that they will lead to key figures.

Trial date

Mr Reid, a Briton converted to Islam, is accused of attempted murder and attempted destruction of an airliner - he is being tried in the United States.

He denies the charges.

Charges against Mr Reid

Attempted use of weapon of mass destruction Attempted murder Attempted homicide Placing an explosive device on an aircraft Interfering with a flight crew (two counts) Attempted destruction of an aircraft Using a destructive device Attempted wrecking of a mass transportation vehicle  Click here to read a profile of Richard Reid

A date for his trial has tentatively been set to start on 4 November - although lawyers will meet again in June for another pre-trial conference.

Mr Reid allegedly tried to set fire to explosives in his shoes while on an American Airlines Paris-to-Miami flight.

He was overpowered by passengers and sedated by an on-board doctor until the flight was diverted to Boston's Logan Airport, where he was arrested.

The FBI says it has discovered forensic evidence that indicates Mr Reid had help making the explosives.

But Mr Reid is said to have told investigators that he acted alone in building the device, using a recipe from the internet.