Police on Tuesday questioned 10 people arrested in anti-terrorist raids in north and central England, but said nothing about what they were suspected of doing.

Nine men and one woman, of North African and Iraqi Kurdish origin, were picked up Monday on suspicion of involvement "in the commission, preparation or instigation of acts of terrorism." Seven were arrested in Manchester, northwest England, and the others elsewhere in the English north and Midlands.

Police did not say whether any explosives had been seized in the operation, which involved 400 officers from five forces, including the anti-terrorist branch of London's Metropolitan Police.

Police refused to comment on newspaper speculation the suspected plot might have been targeting the Old Trafford soccer stadium — home of Manchester United (search) — or the Trafford Center (search), Britain's second-largest shopping mall. Another report suggested a plot involving a target abroad.

Manchester United spokesman Phil Townsend said the team had received no warning from police of a bomb plot.

"We are in discussions with police regarding security at the ground but these are the routine discussions we would have on any match day," he said.

Manchester United, one of the world's most famous soccer teams, is due to play at home on Tuesday and Saturday.

Assistant Chief Constable Dave Whatton of Greater Manchester Police said Monday that the arrests were "part of an ongoing operation" against terrorism.

Under British anti-terrorism laws, suspects can be detained without charge for a maximum of two weeks.

Last month, police arrested nine men and seized more than half a ton of potentially explosive fertilizer in anti-terrorist raids in London and the surrounding area. Six of the men, all British citizens aged between 17 and 32, have been charged with explosives or terrorism offenses.

The seizure of the ammonium nitrate fertilizer — a component of many bomb attacks, including the October 2002 explosions that killed 202 people on the Indonesian island of Bali — spurred intense media speculation about a plot to bomb civilian targets in Britain. Police have released no details of the case against the men.