Mexican journalist Ana Marcela Yarce (L) and Rocio Trapaga Gonzalez are seen in this undated file photo. Mexican authorities are investigating the murder of Yarce and Trapaga Gonzalez whose bodies were found in a park in the south of Mexico City on Thursday. [Photo/Agencies]

MEXICO CITY - Mexican authorities are investigating the murder of two women journalists whose bodies were found in a park in the south of Mexico City on Thursday.

Dozens of journalists have been killed in drug-related violence in Mexico in the past five years. However, the attorney general's office in the capital said the motive for the killing of the two friends was unclear.

"This is still being investigated," a spokesman said, adding that initial findings suggested the victims had been strangled. Both women were 48, the spokesman added.

One of the women, Ana Yarce, was the founder of investigative magazine Contralinea, it said in a statement. The other, Rocio Gonzalez, had worked previously for broadcaster Televisa, the magazine added.

Daily newspaper Reforma said Gonzalez had apparently just withdrawn a large sum of money and the two women may have been victims of a violent robbery.