A speeding rail car on a roller coaster flipped over mid-ride at a Mexican amusement park on Saturday, killing two people and injuring two others. The Mexico City attorney general's office said two men aged 18 and 21 died of head and other injuries when the last car on the coaster derailed at the La Feria amusement park. Two women were hurt.

Preliminary investigations indicate a mechanical failure caused the car to come loose and fall from a height of 33 feet above the ground, said Ulises Lara López, spokesman for the attorney general's office.

Authorities are treating the accident as a case of negligent homicide.

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Video circulating on social media showed the car flipping nearly upside down and smashing into a metal loop on the roller coaster. Images from the aftermath showed first responders attending victims and a single metal rail car on the ground, on its side, near blood stains.

The towering Quimera coaster in Chapultepec Park can be seen from afar in the capital, its three nearly vertical yellow and red loops visible from a major highway. The Feria park closed following the accident.

AP

A vendor at the park told local news outlet El Universal that she saw a passenger thrown from the car, and that other riders hit their heads as the coaster advanced at high speed while dragging the flailing, final car.

The decades-old coaster, like many rides in La Feria, was featured at other parks around the world before finding a home in Mexico City.