Dozens of houses were damaged by a big explosion March 17 that shook a large area of Ha Long Town, one of northern Vietnam's major tourist destinations.
A local resident of Cao Xanh Ward claimed under the condition of anonymity to have seen smoke coming from an empty land plot near their houses before the blast occurred at around 5:10 p.m. Sunday evening.
Dozens of houses suffered damaged roofs, walls and windows. No human casualties were reported.
The explosion created a large hole into the ground and uprooted surrounding trees. It also blew the roofs clear off eight nearby houses.
Hoang Quang Hai, deputy chairman of Ha Long People's Committee, said police identified the cause of the blast to have been a 1-2 kilogram bomb that had been buried underground with a fuse above the surface.
The explosion happened after some residents had burned their garbage there, a regular practice among locals, he said.
Investigators believed that the explosive was left behind by illegal coal miners more than a year ago.
"But there is also possibility that it was hidden by explosive smugglers," Hai said, adding that police had blocked off a perimeter in the area to search for further ordnances that might be present.