Photo: Screenshot of online video

A gas explosion on Sunday in a residential building in Dalian, Northeast China's Liaoning Province, killed two and injured seven. It was the second gas explosion in Liaoning within a week.

The explosion occurred at 5:30 am in a residential building in Wensheng community, Wafangdian, a region that is administered by Dalian. The accident caused two deaths and seven injuries as of press time. The cause of the accident is under investigation, local authorities said on Sunday.

Video circulating online showed it was a five-story building. Plumes of black smoke and open flame were seen at the top of the building after the blast. Roofs and walls on the top floor of the building collapsed. 

Dalian's fire brigade told media outlet btime.com that the explosion occurred on the fifth floor. A total of 28 people were living in the building. The fire brigade dispatched eight firefighting trucks and 40 fire fighters to the scene for rescue work. 

The flames have been extinguished and search and rescue work has ended. The residents who lived nearby have been evacuated to safety, according to official report. 

This is the second gas explosion in Liaoning within a week. On Thursday, a gas explosion that occurred in a restaurant in Shenyang, capital of Liaoning, killed five and injured 47.

Public administration experts said it's possible that aging pipelines in China's old industrial base could explain the frequent gas blast accidents in the province. 

Wang Hongwei, a professor at the Renmin University of China's School of Public Administration and Policy, told the Global Times on Sunday these two cases are most likely to be separate issues in Liaoning. 

Wang said these two accidents could imply the aging of the gas pipelines in the province. Liaoning is one of China's old industry bases and has suffered from resource exhaustion, which could be a deep-seated reason , but exact causes of the accidents should be examined after investigations. 

Previous data showed winter could be a peak season for safety-related accidents, Wang said, suggesting that local departments should strengthen their efforts in supervising safety issues in businesses and residential buildings, and residents should raise the alert toward any potential loopholes.