The word "Muslim" doesn't appear in this story, the reference to police "working closely with the South Asian community" is a coded reference to people who were either born in Pakistan, or in parts of Britain which have been taken over by Pakistanis.
Also, I think "transplanted" might be a better term than homegrown, don't you?
Britain's Home Secretary John Reid said 21 people had been arrested in London, its suburbs and in Birmingham following a lengthy investigation, including the alleged "main players" in the plot. Searches continued in a number of locations.
The suspects were "homegrown," though it was not immediately clear if they were all British citizens, said a police official who spoke on condition of anonymity because of the sensitivity of the case. Police were working closely with the South Asian community, the official said.
The official said the plotters intended to simultaneously target multiple planes bound for the United States.
"We think this was an extraordinarily serious plot and we are confident that we've prevented and attempt to committee mass murder on an unimaginable scale," Deputy Commissioner Paul Stephenson said.ABC News: British Police Thwart Aircraft Bomb Plot