The Irish Air Accident Investigation Unit said it had deployed a team of inspectors to the site of the single-engine helicopter crash.
Police say there are a number of casualties after a helicopter crashed into a building in Ireland.
The crash happened at 3.30pm on Tuesday in Co Westmeath and emergency services are at the scene.
Acting chief fire officer with Westmeath Fire and Rescue Service Pat Hunt told a radio station: "We understand that it’s an incident involving a helicopter crashing into a building in the Joristown Upper townland in Killucan, Co Westmeath."
He added: "All the principal response agencies are mobilising to the scene: An Garda Siochana, the ambulance service and ourselves.
"What we can understand is that there are a number of casualties involved, but again, we cannot at this stage confirm the number."
The Irish Air Accident Investigation Unit said it had deployed a team of inspectors to the site of the single-engine helicopter crash.
Ken Glynn, the mayor of Mullingar-Kinnegad Municipal District, described the incident to Irish broadcaster RTE as "shocking and tragic".
He said his thoughts and prayers are with the families of those involved in the incident.