Zakarpatska, Ukraine: Ukrainian authorities said on Thursday they had detained several members of a French family who tried to smuggle two two-month-old babies across the border hidden under a mattress in their van.

Border guards discovered the twin girls hidden in a chest under a mattress when they inspected the vehicle on the Ukrainian-Hungarian border on Monday, after they became suspicious of a 38-year-old French medic and his father.

The medic said the girls, identified as Vicky and Kim, were born to a surrogate mother in Kiev and that the younger man was their father, according to Ukraine's Border Guard spokesman Eduard Steblyuk.

Steblyuk said the man said he wanted to sneak the children into Europe clandestinely to register them as French citizens, bypassing a local law that doesn't recognise surrogacy.

Border guards decided to search the van because the French men kept turning around to see what was happening inside the vehicle where loud music was playing, and they appeared nervous.

Mahdalyna Vizaver, deputy chief doctor at the Berehivska district hospital that has been taking care of the babies, said they had been well cared for.

"We got them from the ambulance escorted by border guards and customs. They are in good condition. If they crying, it's because they want to eat," Vizaver said.

Doctors initially suspected the babies had been drugged into sleep so that they wouldn't make a noise during the border crossing, but initial tests conducted by the hospital have not confirmed that, Steblyuk said.

Photographs taken by border guards during the detention showed the healthy-looking infants sleeping peacefully in a wooden chest under the bed of the white Mercedes van, bundled tightly in pink and yellow snowsuits and wearing pink caps.

Authorities have launched a criminal probe into illegal transportation of minors abroad.

The two men, whose names have not been released, could face from three to seven years in prison if convicted, Steblyuk said.

Tags: Babies rescued on Ukrainian border, child trafficking, French surrogacy law, twin babies smuggling averted