The surgeon who operated on Tejano singer Emilio Navaira following his band's tour bus crash has warned fans to expect the worst.

The Grammy Award-winning star is in a critical condition following the accident in Houston, Texas, that police say took place at 5am on Sunday morning.

The 45-year-old and his band Rio, who performed in Houston on Saturday night, were travelling on interstate 610 when their bus collided with two other cars, nearly tipping over in the process.

Eight people, including driver Navaira, were taken to the Memorial Hermann Hospital following the incident.

And surgeon Alex Valadka, who performed an operation to remove a blood clot from his brain on Sunday, admits Navaira's fate is now in God's hands.

He says, "We're not even going day by day at this point - we're going hour by hour."

Valadka adds that if Navaira does survive his head injuries, it will take him a "long time" to recover.

(This news article provided by World Entertainment News Network)