Maria Villar, 36, was killed in Mexico after she was snatched from a cashpoint in the city of Toluca, even though a ransom was paid to her kidnappers.
Her body was dumped near the village of Mirasol, near Mexico City, where she lived in an exclusive neighbourhood and worked for computer giant IBM .
The captors are reported to have demanded a ransom of just under £8,000.
German Garcia, the deputy prosecutor for the state of Mexico, revealed she was abducted after taking an unlicensed taxi near her workplace on September 13.
A post-mortem examination confirmed she died the following day after suffocating because of the bag that had been placed over her head.
Her body was found in a stream two days after she disappeared, but investigators only learned she was the victim of a kidnap and ransom plot when her husband and cousin identified her body at a morgue on Tuesday.
Mr Garcia said: “We launched a murder inquiry because we didn’t know she had been kidnapped, although there was evidence, like the chains and the handcuffs, pointing towards that possibility.”
Mrs Villar had been living in Mexico for three years and was a senior executive with IBM, AS Mexico reported.
Her husband, a Brazilian national, was travelling in Spain at the time of the kidnapping, the website reported.
News of the kidnap was kept secret but friends and well-wishers launched a social media campaign for information.
News of Mrs Villar’s kidnap came just days after her uncle, the Spanish Football Federation president since 1988 and a former Athletic Bilbao and Spain midfielder, withdrew from the UEFA presidential election.
He was considered one of the front-runners to succeed the former UEFA boss Michel Platini before he dropped out of the presidential race in a surprise move on September 6.