Rescue workers clear the scene on Sunday after a gas explosion caused a three-story house to collapse in Shanghai, killing two and injuring three. Gao Erqiang / China Daily

The Shanghai government confirmed on Sunday that the explosion of a liquefied gas cylinder caused the collapse of a three-story, wood-frame house that killed two and injured three.

The three injured people were hospitalized, and four others escaped unscathed after the run-down building collapsed at 4:49 am on Sunday, Shanghai's Hongkou district government said in a statement.

The rescue effort was still underway when China Daily reporters arrived at the site in downtown Shanghai at around 10 am. Police cordoned off the block where the building was located, and an ambulance was seen parked nearby. Pictures show the house was destroyed, leaving only a heap of ruins.

Neighbors said the two killed were both male; one was about 70 years old, the other about 50. One of them owns the house and the other was a tenant. Rent of a room in the house cost 500 to 600 yuan ($80 to $96) a month, neighbors said. Local media reported that the younger man was a street vendor who sold fruit.

Yu Qin, 49, who lives about 20 meters away from the house, said that cracks appeared on many of the buildings in the area, including hers, after a high-rise residential project was built nearby.

A security person who worked in a nearby supermarket said that relocation of the area began 13 years ago, but negotiations went slowly over compensation.

The residential area in question is one of the many urban slums in Shanghai. While the city's economic rise over the past three decades moved an unprecedented number of people out of slums, some still live in them today.

Sanitation and fire control are the most serious problems. Residents who live near the collapsed building said multiple fires occurred in the neighborhood over the past few years.

In January, the Shanghai municipal government vowed to demolish 550,000 square meters of urban slums this year, which will cause 24,000 residents to move out. Last year, 31,000 people moved out of urban slums as the government knocked down old houses totaling 746,000 square meters.

The Hongkou district is one of five key areas this year in the government's campaign. Government officials said in 2012 that 62,000 people live in urban slums in the district, totaling 1.52 million square meters.

gaochangxin@chinadaily.com.cn