MAPLEWOOD — A pilot was killed Wednesday when the helicopter he was flying to spray for mosquitoes crashed into the backyard of a suburban St. Paul home.

Police in the city of Maplewood said they got calls about 8:15 a.m. that a helicopter flying low over a neighborhood a few miles east of St. Paul had crashed into the backyard of a private home. Firefighters who were first to arrive at the scene found the helicopter and a detached garage in flames and the pilot dead in the wreckage.

Maplewood acting Police Chief Dave Kvam identified the pilot as Michael Kramer, 44, of St. Charles. He was alone in the helicopter, Kvam said, and no one was in the house or garage at the time of the crash.

“I heard a big noise and didn’t know what it was,” said Donna Basler, 70, who lives four houses from the crash site.

“Then my neighbor called and said there’s a big fire.”

Firefighters quickly extinguished the blaze, which did not spread to the house. The garage was damaged but was still standing.

The National Transportation Safety Board will lead the investigation. Investigator Aaron Sauer said it could take six months to a year to determine what caused the crash. He said the agency would examine autopsy and toxicology results on Kramer, and look into his training and a number of other factors that could have contributed to the crash.

Lt. Kerry Crotty of the Maplewood Police Department said the helicopter did not crash directly into the garage but she believed several of its rotors struck the structure as it was crashing into the ground.

The helicopter, owned by Scott’s Helicopter Service in Le Sueur, had a contract with the Metropolitan Mosquito Control District to spray for mosquitoes. Jim Stark, executive director of the district, said it would temporarily suspend its spraying. Kramer was an employee of the helicopter company.

Neighbors said the small helicopter was swooping very low over the area before the crash, but that’s not necessarily unusual for helicopters that spray for mosquitoes.

“They do fly at relatively lower altitudes, lower air speeds, and over residential communities,” Sauer said.

The neighborhood backs up against a small but heavily wooded nature preserve. The crash happened about a block from heavily traveled Century Avenue, a major north-south thoroughfare in the suburbs east of St. Paul.