SAUK RAPIDS (AP) - Air traffic controllers' communications could provide insight into the cause of a plane crash that killed the pilot and passenger in Sauk Rapids.

Federal investigators are trying to determine what caused the small plane to crash into a house last Friday, killing the pilot, Scott Olson, and 16-year-old foreign exchange student Alexander Voigt.

St. Cloud Regional Airport director Bill Towle says Olson was required to contact controllers after taking off, but once he was outside the airport's controlled air space, he wasn't required to maintain communication. Investigators will also look at what communication controllers had with an Allegiant Air flight in the area of Olson's plane just before the crash.

Towle says the Allegiant pilot would be required to contact the control tower before it entered the airport's air space.