Personnel from the HCMC Department of Science and Technology take samples near a sinkhole on Binh Loi Street, Binh Thanh District, HCMC / PHOTO COURTESY OF VNEXPRESS
Authorities in Ho Chi Minh City have been contradictory in their conclusions on the cause of a mysterious explosion on a local street that created a sinkhole spewing fire and smoke early this week.
On Friday ,VnExpress online newspaper quoted the HCMC Department of Science and Technology as saying that the explosion on Binh Loi Street, Binh Thanh District was possibly caused by the accumulation of methane gas under the ground.
Department officials said they detected methane with the content of 0.2-2 percent in eight gas samples taken near the hole, while soil and water samples contained nothing abnormally high.
Analysis of air samples found all indexes within allowable limits, they added.
According to the officials, Binh Loi used to be a swamp full of methane. When accumulated to a certain level and sparked by a heat source, the gas could cause explosion and fire, they said.
Officials believed that the amount of gas was not high, given that the fire and smoke stopped after spewing for around 24 hours.They said it was likely that all the gas has been released already.
The hole, which appeared on October 28, was 20 centimeters in diameter and 30 centimeters in depth, according to the report.
Locals said it kept bubbling and smoking through the day, sometimes spewing bluish fire as high as one meter. They also say it produced a minor explosion the next morning.
On the other hand, the Police Department's Firefighting Division said they did not detect any flammable gas at the hole, but a system of electrical wires which were burned and broken, implying that there was an electrical accident.
Police said an excavation by a street contractor about two months prior had possibly damaged the wires' insulated covers, leading to an electrical leak and finally the explosion.
The wires were located 40 centimeters underground, while the hole had a 33-centimeter diameter at its mouth, 25-centimeter diameter at its bottom, and a 50-centimeter depth, according to police.
Speaking to Thanh Nien, Nguyen Van Manh, who lives near the incident site, said electrical devices in his neighborhood had been operating unsteadily since October 26, and there was an outage that lasted a few hours the next day.