ALBUQUERQUE, United States (AFP) - Johnny Tapia's family, already grieving over the former world champion fighter being hospitalized after an apparent drug overdose, now has two deaths to mourn as well.

Two members of the US fighter's family were killed on Tuesday in a car crash while on their way to visit Tapia in the hospital.

Tapia's brother-in-law Robert Gutierrez and nephew Ben Garcia were killed when their car overturned on an interstate highway. Police said Gutierrez, 39, and Garcia, 23, were thought to be bound for Albuquerque Presbyterian Hospital.

Speed was a factor in the deaths of both men. They died at the scene of the crash, about a three-hour drive north of Albuquerque, after being thrown from the car.

Tapia was rushed to the hospital in critical condition on Monday after being found unconscious in a motel room.

His wife Teresa told police "I think my husband overdosed on something," and police plan to charge Tapia with possession of a controlled substance.

The five-time former champion in the super flyweight, bantamweight and featherweight divisions was upgraded on Tuesday to serious condition.