SANTIAGO (Reuters) - Two explosive devices were detonated within a span of 24 hours in the Chilean coastal city of Vina del Mar, causing at least three minor injuries, in the same week the Andean country suffered its worst bomb attack in at least 20 years.

The second device exploded Wednesday evening in the bathroom of a supermarket, leaving two people with minor injuries, after a similar explosion Tuesday night left a woman with trauma to her hearing.

Chile is on high alert after Monday's attack, when a bomb was left in a trash can near a metro station in capital city Santiago, wounding 14. No one has claimed responsibility, and police say they do not know who was behind it.

The explosive devices in Vina del Mar were made with a plastic bottle, acid and foil, police officials said, adding they did not contain shrapnel and caused only noise.

"Again a device exploded, this time in the public bathroom. Due to this we sent two people to the hospital for preventive care as they showed symptoms of hearing damage," said police official Rodrigo Loyola. "No other injuries or damages were reported," he added.

Tuesday night's explosion inflicted light trauma to the hearing of a woman that was moving the trash can where the device had been planted.

(Reporting by Anthony Esposito and Rosalba O'Brien; Editing by Lisa Von Ahn and Cynthia Osterman)