Three members of a family vacationing in southern Spain drowned after becoming trapped in a swimming pool, prompting an investigation into a potential malfunction with a drainage mechanism that may have sucked them underwater, the authorities said on Wednesday.

The tragedy unfolded when a 9-year-old girl began having difficulties in the pool. When her father jumped in to rescue her, he then became trapped, too. Another family member, a 16-year-old, then entered the water to help, but all three died, said Jorge Martín, a spokesman for the Civil Guard of Malaga Province, where the accident happened.

The father and daughter were British citizens and the teenager was American, the authorities said. No further details were given about them, though five members of the family were said to have arrived in the town of Mijas on Saturday.

Accidents linked to faulty drainage or pumping systems in pools have happened before. In 2002, a 7-year-old girl from McLean, Va., drowned in a spa when she became entrapped by the powerful drag of a portal sucking water into a filtration system, and a man and three children died at a water park in Texas in 2004.