A 38-year-old woman has been arrested at Heathrow Airport for conspiracy to commit female genital mutilation (FGM), Scotland Yard said.
The British national was held after arriving on a flight from Sierra Leone and taken to a west London police station where she remains in custody.
A 13-year-old Sierra-Leonian girl travelling with the woman was taken into the care of social services.
Metropolitan Police, Border Force and National Crime Agency (NCA) officers today concluded a week-long initiative at Heathrow aimed at preventing and detecting FGM.
The woman, who was born in Sierra Leone, was arrested during yesterday's initiative, during which officers spoke to 36 individuals who had alighted from two flights from Nigeria and from Liberia, via Sierra Leone.
A Nigerian female, whose age is yet to be established, was also taken into the care of social services as a potential victim of trafficking. An investigation by Border Force is going on but is not related to FGM offences.
Speaking at Heathrow Airport this week, Metropolitan Police commissioner Sir Bernard Hogan-Howe said m andatory medical examinations to identify FGM victims may have to be considered in the UK.
He said there had been a lack of referrals from schools and medical professionals about girls who had undergone the procedure, as an operation was launched at airports to identify possible victims.
An estimated 66,000 women in the UK have undergone FGM and more than 20,000 girls under 15 are thought to be at risk of the practice, which is classed as torture by the UN.
The first UK prosecution for alleged FGM began earlier this year, while there have reportedly been 100 FGM-related convictions in France.
Police launched Operation Limelight this week at airports across the country, targeting flights to and from countries known to carry out FGM.
The joint-force operation included officers at Heathrow Airport speaking with passengers on 13 outbound flights to "high risk" countries.
High-risk countries include Somalia, Sierra Leone and the Democratic Republic of the Congo.
Passengers were warned that FGM is illegal in the UK and, if caught, offenders face a large fine and a prison sentence of up to 14 years
Prior to this week's operation, there had been 190 referrals to the Met since 2010. In relation to those 190 referrals, 12 arrests have been made.
The majority of referrals do not relate to specific allegations that FGM has taken place, but instead refer to safeguarding concerns.
Sir Bernard said: "They have a slightly different system in France so they can have mandatory medical examinations.
"We believe that's one of the things that makes a difference for them.
"We have to rely on getting our message out through the media and encouraging members of the public to come forward."
Asked whether mandatory medical examinations should be introduced in the UK, Sir Bernard replied: "It's one of the things, I think, probably the Government is going to have to consider at some point.
"I think the first thing we have to do is make sure we've explored all opportunities the existing legislation provides."
Sir Bernard said it was important for schools and medical professionals to contact police with information about FGM victims to ensure those responsible were prosecuted.
He said: "We're not getting an awful lot of referrals from the community, from medical professionals or from educational professionals.
"We need those because without that we can't start an investigation.
"Of course, the victims could come forward eventually.
"But what we do know is that's quite difficult.
"If you have to report against your parents, that's obviously quite a challenge.
"It's really important they understand the barbarity of this act and it is a criminal offence which is punishable by 14 years' imprisonment."
The week-long initiative at airports across the country aimed to identify girls who might have been mutilated as well as warning UK passengers that it was illegal to arrange for a child to be flown abroad for the procedure.
Detective Chief Superintendent Keith Niven, head of the Met's sexual offences, exploitation and child abuse (SOECA) command, said: "FGM is an abhorrent offence which includes violent assaults upon children.
"This is an illegal practice and it will not be tolerated in the United Kingdom.
"It's really important to educate people who engage in this practice so they are aware that this is not a legitimate way to bring children up.
"This is child abuse... and people will be prosecuted if we find evidence of this."
Operation Limelight was supported by UK Border Force and the National Crime Agency, as well as officers from the Met, Essex, Avon and Somerset, Greater Manchester, West Yorkshire, Sussex and West Midlands Police.