A nearly 60-foot segment of an expressway in a rural area of southeastern China collapsed before dawn on Wednesday after days of heavy rain, killing 24 people and injuring 30 others.

Photos released after the incident appeared to show that a landslide had begun under two lanes of an expressway that ran along the side of a hill. A wide, brown scar of mud ran down the side of the hill between bright green foliage, leaving a large gap in the expressway.

Vehicles lay jumbled at the base of the hill below the hole, blackened and still smoking from a fire that had burned vigorously during the night, drawing a large number of fire trucks to the area.

The state news media said that many of the survivors were seriously injured, with drivers and passengers alike suffering severe bone fractures and injuries to internal organs.

A witness told the state news media that he had heard a loud bang and briefly struggled to retain control of his car. He then realized that the road had collapsed right behind him and cars following him had disappeared into the void.

Expressway traffic is especially heavy across China with the start of a five-day national holiday on Wednesday. The section of expressway that collapsed was on the eastern outskirts of Meizhou, a city in Guangdong Province. Many victims were on their way to the neighboring Fujian Province as the holiday began.

More than 500 rescuers from the police as well as emergency and other departments were deployed. The local traffic police sealed the expressway off from traffic in both directions.

Much of the northeastern corner of Guangdong, where the accident occurred, is rugged country with hilly terrain. Another section of the same expressway was briefly closed in April last year after a landslide covered the road with mud. No death or injuries were reported then.

A continuous accumulation of humid and warm air, coming from the South China Sea to the southwest, has left southern China with a prolonged period of severe weather in the past two months. The Central Meteorological Observatory issued orange warnings, the highest level for severe weather, seven times in April.

On Saturday, a rare tornado and a hailstorm swept neighboring Guangzhou city, a production hub in southern China, killing five and injuring 33. And on Tuesday, Shenzhen Airport issued an orange warning for large-scale flight delays for the first time this year.