Four people have been confirmed dead after a small twin-engine plane crashed into two homes in East Haven, Conn. on Friday morning.

Bill Henningsgaard, a 54-year-old former Microsoft executive, and his 17-year-old son Maxwell were confirmed by family members to be the deceased pilot and passenger of the plane, USA Today reports.

Thirteen-year-old Sade Brantley and her one-year-old sister Madisyn Mitchell, who lived in one of the houses and were unaccounted for after the accident, were confirmed dead, according to New York Magazine.

The Henningsgaards were reportedly on an East Coast college tour.

The fire that resulted from the crash was reportedly so extensive, firefighters were prevented from immediately searching for victims, CNN reports. “It’s…total devastation in the back of the home,” said East Haven Mayor Joseph Maturo Jr.

The mother escaped the house but was unable to rescue her children.

Authorities are unsure of what caused the plane to crash. Henningsgaard had been communicating with air-traffic control but did not issue a distress call.

The plane missed its initial approach to land at Tweed New Haven Airport, and crashed during its second approach around 11:25 am.

“They fly in very low, and a lot of times you can hear the engine cut off before it gets to the runway,” explained the airport manager, Lori Hoffman-Soares.