A woman in a blonde wig is suspected of carrying out a hit on two alleged Israeli underworld figures in a busy restaurant in Mexico City.
Alon Azulay, 41, and Benjamin Yeshurun Sutchi, 44, were shot dead on Wednesday as fellow diners looked on.
The woman, who was arrested as she attempted to flee, told police it was a crime of passion.
But police are now investigating if it was actually a “settling of scores” between rival criminal gangs.
“The passion motive has been discarded,” Ulises Lara, a spokesman for prosecutors in Mexico City, told reporters on Thursday.
“The event yesterday lead us to link the events to a settling of scores between criminal groups.”
Israel’s embassy in Mexico said the men had criminal records in both Israel and Mexico, while Israeli local media has claimed Sutchi was well-known within Israel’s criminal underworld.
Police sources told Ynet they were in no doubt it was an “assassination” ordered by another Israeli.
However, the woman, named in Mexican media as Esperanza N, 33, told police she had attacked the men after a romantic relationship which began on social media turned sour.
She was caught as she fled the scene, trying to change clothes and discard her disguise, according to local reports.
Police, who are investigating possible links to drug trafficking, arms sales or money laundering, have also said they believe she was working with at least three accomplices.
A gunman shot and wounded a police officer outside the shopping centre where the attack took place.