As part of an international effort to track down those responsible for the Sept. 11 attack on America, British police on Saturday were continuing to hold four people who were arrested in connection with the case, reports CNN. Police apprehended two men and a woman in west London in a 3 a.m. Friday raid, and then arrested a fourth man in the West Midlands around 7 p.m., said Scotland Yard. Nationalities of those arrested were not revealed, nor was an explanation of their possible link to the case. All four were being questioned in a central London police station, police said Saturday. Of the first three arrested, said the cable news station, a man, 27, and a woman, 25, were living together at one residence, while another man, 29, was picked up at another residence. The fourth man, in his mid-40s, was picked up in Birmingham, the UK's second largest city and one with a large ethnic population, noted CNN. It also pointed out that police can detain suspects for 48 hours before having to apply to the courts for an extension and after seven days officers have to decide whether to charge or release. Also reported: Seven people were arrested outside Paris on Saturday, reputedly with plans to blow up the U.S. Embassy there. Other suspects are reportedly being held in Canada and Europe, as well.