London (CNN) -- Eight people in custody as part of the wide-ranging investigation into failed car bombings in London and Glasgow all have links to the medical profession.
Police patrol Glasgow Airport as Britain's terror alert remains at a critical level.
Seven are doctors or medical students and the eighth is a laboratory technician. Two other doctors are being questioned about the case but are not in custody.
The investigation moved halfway around the world Tuesday to Australia, where authorities are questioning two doctors who were recently recruited from Liverpool, England, Australian officials said.
One of the men, an Indian national, was taken into custody at Brisbane's airport as he was trying to fly out, the officials said. He was reportedly holding a one-way ticket to India at the time.
He was identified by sources close to the investigation as Dr. Mohammed Haneef, 27. He had a temporary visa and worked at a hospital in the Brisbane area, where his office was searched by police, authorities said.
Haneef had previously worked at Halton General Hospital near Liverpool where another doctor -- identified by British media as Sabeel Ahmed, who was taken into police custody late Saturday -- was employed, according to hospital and police officials.
Both Ahmed and Haneef graduated from Rajiv Ghandi University of Health Services, British media reported.
Haneef was described by his Australian colleagues as a good employee in the emergency department and was "regarded as a model citizen, excellent references," according to Queensland Premier Peter Beattie.
Another doctor is being questioned by Australian authorities, but is not formally in police custody, Beattie said.
Both that doctor and Haneef had been recruited to work in Brisbane last year through an ad in the British Medical Journal, Beattie said.
In Britain, seven people are in police custody in connection with the terror probe, including the two men believed to have carried out the attempted car bombings.
Iraqi doctor Bilal Abdulla, 27, has been identified by sources as one of the two men who drove a car packed with explosives and gas canisters into Glasgow's airport on Saturday.
The second man, identified by sources as Dr. Khalid Ahmed, was severely burned in the Glasgow attack and is in critical condition at Royal Alexandra Hospital in the Paisley section of Glasgow.
No one else was seriously hurt in the attack.
Police had been tracking both men after linking them to the two car bombs parked in central London on Friday.
The two men shared a rental house about two miles from Glasgow's airport, which police descended upon hours after the Glasgow attack, the leasing agency told CNN.
Police had contacted the leasing agency about 15 minutes before the attack asking about a mobile phone number they had possibly gleaned from a cell phone found in one of the London car bombs.
British police and security sources told CNN that they believe the two car bombs were set to be remotely triggered, possibly by mobile phones, but failed to detonate.
British media reports say Abdulla worked as a doctor at Royal Alexandra, which has become a focus of the terror investigation.
Two of the suspects, identified only as men ages 28 and 25, were detained at the hospital on Sunday during a search of the doctors' quarters. Sources close to the investigation said that the two are Saudi nationals and were medical students.
In addition to searching the hospital, a police bomb unit has carried out several controlled explosions of suspicious items outside the medical facility in the past 48 hours, including at least one car.
Britain is at its highest terror alert following the attempted terror attacks over the weekend.
Early Tuesday, police detonated a suspicious vehicle at a Glasgow mosque while transport police in London detonated a suspicious package found outside the Hammersmith underground station in west London.
Hours after the Glasgow airport attack, undercover police in northern England arrested Dr. Mohammed Asha, a 26-year-old Jordanian physician, along with his 27-year-old wife Marwa Dana, in a dramatic raid on the M6 highway in the Cheshire area, according to his family and a source close to the investigation.
It is unclear what role police believe Asha played in the terror plot. His family in Amman, Jordan described Mohammed Asha as a top medical student and insisted that he could not be involved in such a plot.
"We can't believe it," his older brother Ahmed told CNN's Cal Perry. "Mohammed didn't make any difference between the Christians and the Muslims, and he has a lot of Christian friends."
The family is especially worried about Asha's 2-year-old son, who was born in Britain shortly after the couple moved there. The family does not know who is taking care of the young boy since both parents have been arrested, the brother said.
Sources close to the investigation said that Marwa Asha is a laboratory technician.
Asha's house in Newcastle-under-Lyme in North Staffordshire has been searched for the past few days.
Neighbors there told CNN's Matthew Chance that another doctor of South Asian descent is also part of the probe.
Police sealed off the home of that unnamed doctor and his wife, which is about two miles from Asha's home. Forensic teams are searching the house, where the doctor and his wife have lived for about a year, neighbors said.
It is unclear if the doctor and his wife are in police custody. Police would not confirm any details about their search.
So far, police have raided at least 19 locations across Britain as part of the "fast-moving investigation," newly appointed British Home Secretary Jacqui Smith said Monday. E-mail to a friend
CNN's Nic Roberston, Paula Newton, Jonathan Wald and Andrew Carey contributed to this report.