(Photo: CGTN)

A couple detained in Mexico while transporting human body parts in a baby carriage has admitted killing 20 people, twice the number originally suspected, the chief investigator on the case said on October 9. 

The man also admitted raping some of his women victims and selling some of their body parts, said state prosecutor Alejandro Gomez of Mexico state.

The man and woman were arrested Thursday in Ecatepec, a violence-hit suburb northeast of Mexico City, on suspicion of killing 10 women.

The man gave detailed accounts of those 10 murders, and told investigators that he and his wife had killed 10 other people as well, according to Gomez.

Prosecutors are now trying to establish whether that is true, or the boast of a "psychopath" and "serial killer," he said.

"He wants people to see his picture, to know his name ... I would obviously classify this person as a murderer, a serial killer."

It's reported that the couple also admitted to selling the two-month-old baby of one of their victims to another couple, who was also arrested.

The arrested suspects are being identified only as Juan Carlos "N" and his wife, Patricia "N", in accordance with Mexican law.

The couple were living with their three children, including a baby.

When authorities searched their two houses, they found human remains in cement-filled buckets and wrapped in plastic bags inside a refrigerator, as well as articles of clothing apparently belonging to some of their victims.

The man told investigators that he and his wife lured their victims, many of whom were young mothers, by offering discount clothing for their babies.

"They were single mothers ... and they needed someone who could help them find inexpensive baby clothes," said Gomez.

Investigators tracked down the couple by tracing cell phone calls the missing women had placed to them, he said.

The case has triggered shock in Mexico. Hundreds of people protested in Ecatepec on Sunday, carrying candles and white flowers to demand action by the authorities to deal with an explosion of violence against women and girls.

Seven women and girls are killed in Mexico every day, according to UN Women.

Across Mexico, there were a record 28,702 murders in 2017. The number has surged since 2006, when the government deployed the army to wage war on the country's violent and powerful drug cartels.