London ? At least three physicians were identified Monday among suspects arrested in Britain’s failed car bomb attacks, and authorities announced three new arrests – including a doctor in Australia – as the investigation spread overseas.

British media reports said an Indian doctor also was among the eight people in custody and another outlet said at least five of the detainees in Britain were physicians. British police confirmed a Palestinian doctor and Iraqi physician were among those held, while Australian officials said a foreign doctor working there had been detained in the case.

Officers used heightened stop-and-search powers and armed response vehicles to hunt for anyone else who might have been involved in the plot, and police put on a show of force to bolster security at airports and train stations and on city streets.

Hours after police announced the arrests of two more people in the Glasgow area, officials said an eighth suspect was detained “abroad by local authorities” Monday.

Australian authorities later said he was arrested at the airport in the eastern city of Brisbane while trying to leave the country. Queensland state Premier Peter Beattie described the suspect as a 27-year-old man but withheld his identity. Beattie said he was a “model citizen” with “excellent references.”

Australian police are questioning a second doctor about the failed terrorist attacks, Beattie said. But authorities were not aware of any specific link between the second doctor and the foiled attacks.

Australian Attorney General Philip Ruddock said the suspect arrested at the airport was a doctor at a hospital in Queensland state and was not a citizen. Authorities said he was recruited in Liverpool, England, but completed his medical internship in India.

A British security official said earlier in the day that Pakistan and several other nations were asked to check possible links with the suspects. British-born terrorists behind the bloody 2005 London transit bombings and others in thwarted plots here were linked to terror training camps and foreign radicals in Pakistan.

“We have asked partners overseas to check possible links, and that work has begun,” the security official said, adding that it was still possible some British-born people were involved in the plot. The official spoke on condition of anonymity because of the sensitivity of the case.

Authorities said police searched at least 19 locations as part of the “fast-moving investigation,” which has come at a time of already high vigilance before the anniversary of the suicide bombings in London that killed 52 people on July 7, 2005.

Prime Minister Gordon Brown, who has said the group behind the weekend attacks was “associated with al-Qaida,” received a call from President Bush commending him for Britain’s response.