Two commuter trains collided in a tunnel outside Caracas, killing at least one person, injuring about 30 and leaving frightened passengers gasping for air in the dark, officials said.

One train suddenly braked due to an apparent malfunction and another crashed into it from the rear on Thursday, causing the first to derail, Transportation Minister Francisco Garces said on state television. Officials said a packed train coming in the opposite direction was able to stop before colliding with the others, averting a possible disaster.

The crash apparently cut power in the tunnel between Caracas and the suburbs of Los Valles del Tuy.

Passengers “remained inside the wagons without air conditioning and within the tunnel,” causing some to feel a sense of suffocation, said Victor Lira, civil defence director for Miranda state.

He said five people suffered scrapes or trauma while the rest were treated for respiratory problems or high blood pressure.

Mr. Lira said the engineer of the rear train died. President Hugo Chavez said he regretted the accident. He urged Venezuelans not to speculate about possible causes but to await the results of an investigation. “I lament the death of an employee, the driver of the train,” Mr. Chavez said.

The injury toll was low in part because the trains that collided were almost empty, heading out of the capital as rush hour traffic flowed the other way, Mr. Lira said. He said one of those trains had about 40 passengers on board, while the other wasn’t carrying passengers.

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