Three men were hospitalized when a single-engine plane crashed Sunday upon taking off from Danbury Airport, officials say.

Fire officials tell News 12 that one person is in critical condition with life-threatening injuries. Another person is in serious condition, and the third suffered minor injuries. All three were taken to Danbury Hospital, but the victim with the most serious injuries has since been transferred to Westchester Hospital.

Authorities say the initial 911 calls reporting the crash came in around 10:25 a.m.

The plane crashed on a hill near the airport property, behind the Danbury Dog Park. A deputy fire chief says that first responders had to beat their way through the brush on the hill to make it to the plane and get the victims out of the wreckage.

The men were flying in a four-passenger Cessna Skyhawk. They had rented the aircraft Sunday morning and were heading west, although authorities have not yet confirmed their exact destination.

The identities of those who were injured have not yet been released. 

The Danbury Dog Park was closed following the crash. Officials say the dog park will remain closed until crews are able to remove the wreckage of the plane. Machinery was brought in Sunday afternoon to clear a path to the plane through the rough brush and terrain.

The FAA, NTSB and the airport administrator are investigating the cause of the crash. Officials say the plane had a full tank of gas.