Madonna is expected to arrive in Malawi Sunday, airport officials said, as the star's plans to adopt a girl as her second child from the poor African country began to draw criticism.

Officials at the airport in the capital spoke Saturday on condition of anonymity due to the sensitivity of the subject.

The luxury lodge where Madonna has stayed in the past has been fully booked and casual visitors have been turned away. International media have begun arriving in the capital in anticipation of her visit.

Friday, a welfare official and a person involved in the adoption proceedings said the singer plans to adopt a 4-year-old girl.

But a British children's charity has urged Madonna to "think twice" before adding another African child to her celebrity family.

Save the Children UK said Saturday that the recently divorced star risked sending the wrong message by going through with the adoption.

Spokesman Dominic Nutt said many international adoptions are unnecessary — and some even feed into a criminal "adoption industry."

Nutt said he was not suggesting that Madonna was doing anything wrong — but he said the whole process of international adoptions is often flawed.

He said that, barring exceptional circumstances, children should be kept in the care of their extended families or within their communities.

Madonna's spokeswoman Liz Rosenberg in New York, who has not commented on the adoption reports, told The Associated Press on Saturday that the star would not respond to Save the Children.

The welfare official and people close to the case, who spoke on condition of anonymity due to the sensitivity of the subject, said the girl's mother, an unmarried 18-year-old, died a few months after the child was born. Her father is believed to be alive but no other details were available.

The girl's relatives at first resisted the adoption but have now consented, they said.

Madonna and the girl's uncle are expected to appear in court on Monday to sign adoption papers.

Madonna was harshly criticized for her adoption of David Banda, now 3, in 2008. Children's advocacy groups accused the 50-year-old star of wielding her wealth and influence to circumvent Malawian law requiring an 18- to 24-month assessment period before adoption.

Austin Msowoya, legal researcher with Malawi's Law Commission, played down concerns that a second adoption by Madonna would violate any laws.

He said the best interests of the child needed to be taken into account — whether this was staying in an orphanage in Malawi or getting "an education with Madonna."

"When you look at these two options, then perhaps it becomes in the best interests of the child to allow the adoption if the parents and the guardians consent to it," he told Associated Press Television News Saturday.

Reports that Madonna wants to adopt a girl from Malawi have been circulating for some time. But the first official hint came from the star herself last week.

In an interview in Malawi's leading daily The Nation, the singer said she was considering another adoption but would only do it if she had "the support of the Malawian people and government."

If the adoption goes through, Madonna would become a single mother of four. She also has an 8-year-old son, Rocco, with former husband Guy Ritchie and a 12-year-old daughter, Lourdes, from a previous relationship.

Madonna first traveled to Malawi in 2006 while doing charity work and filming a documentary on the devastating poverty and AIDS crisis there. She is also establishing a school for girls there.