Thai authorities are investigating the discovery of nine surrogate babies in a Bangkok condominium that are believed to share the same Japanese biological father, police said on Thursday.

The case is the latest to emerge after an Australian couple were accused of abandoning a Down syndrome baby to the Thai birth mother, triggering global condemnation and calls for an overhaul of lax surrogacy laws.

Authorities acting on a tip-off raided the condominium in the Lat Phrao area of the Thai capital on Tuesday and found nine babies being looked after by seven nannies, with a pregnant 20-year-old also living there.

Police spoke to a Thai man who said he was the lawyer of a Japanese businessman who claims to be the babies' biological father, said deputy national police chief Aek Angsananont.

"We are questioning the nannies, as well as asking for cooperation from the Japanese embassy, to help conduct DNA testing," Aek told Reuters.

He added: "If the Japanese man admits that all the children are his babies, we would ask him why he wanted to have so many."

Reuters was unable to contact the lawyer, Ratprathan Tulathorn, despite repeated attempts to reach him.

The latest case has raised concerns over the ease with which foreigners can come to Thailand to buy surrogacy services. The country has no laws directly relating to the practice.

Although commercial surrogacy is barred by the code of conduct of the Medical Council of Thailand, the country is a top destination in Asia for fertility clinics and couples opting for surrogacy arrangements.

An official at the Ministry of Social Development and Human Security who is part of the team investigating the latest case said the nannies were hired for a monthly compensation of 10,000 baht ($310), while the pregnant woman said she was hired for 300,000 baht to give birth.

"We are looking for evidence to determine whether this surrogacy case is illegal," said the official, who declined to be named because he was not authorized to speak to the media.

Pedophile found

Australian authorities said on Thursday they had finally contacted a man at the center of a Thai surrogate-baby scandal. He was exposed in the media as a convicted pedophile. His son defended him as a changed man.

Child-protection officials had been trying to contact the man and his wife since Tuesday, but visits to their home in Bunbury, south of Perth, were fruitless.

The man, 56, sparked global controversy for apparently abandoning his Down's syndrome baby boy, Gammy, in Thailand and taking only his healthy twin sister back to Australia, although he and his wife dispute the circumstances.