The girls, born last month in the northern province of Shaanxi, were allegedly victims of the same female doctor who sold a baby boy reunited with his parents earlier this week.
The obstetrician, Zhang Shuxia, told the twins' mother in the delivery room that her babies had "deadly congenital diseases" and convinced her give them up, China National Radio reported.
Zhang also said their arms and legs were "broken" and stopped other relatives seeing them, the report added.
The doctor and two other suspects were detained after the boy's family became suspicious and reported their case to police. The blaze of publicity surrounding his recovery has prompted a wave of others to come forward.
One of the girls was found in Shandong province, more than 500 kilometres from her birthplace in Fuping county, and her sister around 160 kilometres away in Shanxi province, the website of the People's Daily said citing local authorities.
Police had received reports of 55 possible incidents yesterday, including 26 allegedly involving Zhang, it added.
Lou Qinjian, governor of Shaanxi, yesterday called the case "vile" and vowed to punish those responsible "seriously", it said.
Fuping is the home county of the family of Chinese president Xi Jinping.
Trafficking of children is a serious problem in China, blamed in part on the "one-child" policy which has put a premium on baby boys, with girls sometimes sold off or abandoned.
In a much publicised case, Chinese police rescued 89 children and arrested 355 suspects in December after breaking up a series of child trafficking rings.
