High-profile Mexican kidnapping over

Laura Zapata was the first sister to be released

Kidnappers have released the Mexican writer, Ernestina Sodi, sister of the singer and actress, Thalia.

She disappeared more than a month ago along with her other sister, Laura Zapata, after leaving a theatre in Mexico City.

Thalia, a popular singer, is married to Sony Music boss Tommy Mottola

Officials say she was freed on Saturday - 18 days after her sister - but the circumstances surrounding the end of the kidnapping ordeal are unclear.

Neither of the kidnappings was reported to the police, with correspondents saying that families involved in Mexico's frequent abductions often prefer not to involve authorities to prevent them intervening and possibly leading to their relatives being harmed.

The kidnappers are reported to have demanded a ransom of $1m for the sisters' release following their abduction on 22 September.

The family is believed to have conducted its own negotiations with the kidnappers.

Thalia is married to the head of Sony Music and has performed at the Latin Grammys.

Writer 'recovering'

Ms Sodi, who had recently co-written a book about Mexico's presidential residence, was recovering at her home, said her sister, Ms Zapata who is an actress.

[The abduction] totally changed our lives

Laura Zapata

In a telephone call to Televisa news presenter Joaquin Lopez Doriga late on Monday, Ms Zapata expressed thanks to Mexicans for their good wishes but said that the family had been "devastated by this experience".

"It totally changed our lives. There is the us of before 22 September and the us of after 22 September," she said.

Ms Zapata declined to let her sister speak on the phone, saying: "She is in a very altered state."

But she said both had been treated relatively well by their abductors.