Washington, Mar 5 (IANS): At least 14 people were injured and over 200 people others displaced following an explosion that destroyed parts of an apartment building complex in the US state of Maryland, officials said.

Three of the injured remain in serious condition, while all residents of the four-storey building in Montgomery County, just several kilometres outside of Washington, D.C., have been accounted for, Xinhua news agency quoted the officials as saying to the media on Friday.

Montgomery County Fire Chief Scott Goldstein said three of the six buildings in the complex have been declared unsafe to occupy, as emergency crews continue to search through the debris.

Investigators reportedly believe a maintenance man accidentally cut a gas line, instead of a drainpipe, releasing gas likely to cause the explosion.

"That is an investigative theory along with several others until we get through all of the debris and a thorough examination of the building," Goldstein said.

"We cannot rule out any of our active theories and cannot identify that that was the cause of the explosion."

Firefighters rushed to the scene on Thursday morning and were able to help some residents escape before the apartments were consumed by fire and collapsed.