A helicopter crashed in the middle of a residential neighbourhood in Cranbrook, B.C., on May 13, killing four people. (Submitted by Larry Belzac)

A loss of power to its engine and rotor prompted a helicopter to crash three months ago in a residential area in Cranbrook, B.C., killing four people, a spokesman for the Transportation Safety Board of Canada said.

The May 13 incident killed three people on the aircraft and one person on the street when the plane hit the ground and burst into flames. The chopper was being used by BC Hydro to inspect power lines.

Investigators believe a problem with the engine components cut power to the engine and rotor, Bill Yearwood, regional manager with the Transportation Safety Board, told CBC News.

"We have determined the engine components and rotating components are consistent with power loss," Yearwood said. "Our efforts are … determining why it lost power."

The engine components are being examined at a laboratory in Ottawa, he said.

"We need to determine if those anomalies were caused by fire damage or before the accident," Yearwood said.

BC Hydro is conducting its own investigation into the crash, spokeswoman Susan Danard said.

The utility company has suspended the use of choppers over residential areas for inspection purposes until it has completed its investigation, she said.

With files from Bob Keating