Two firefighters had to be treated at the scene of an apartment building fire Easter morning in Walden that displaced at least four residents, according to police.

Authorities say the fire at 54 Walnut Street caused a propane tank to explode. The blast was significant enough for neighbors to feel it from inside their homes.

Most of the damage is to the front of the building, which is charred and remains blocked off with police tape as of Monday morning.

A viewer alerted News 12 to the blaze and sent in a photo of the scene showing the front portion of the house engulfed by flames.

Village of Walden police say the building has three apartments and that four people were inside at the time of the fire at approximately 6 a.m. but escaped unhurt. They say the firefighters hurt were treated for exertion and a wrist cut.

The house is across the street from Most Precious Blood Catholic church. The church’s priest lives nearby and was there as rescuers arrived.

“I just heard a loud crack and an explosion,” said Tom Colucci. “I thought it was a car accident then I looked out the window and I saw some smoke and people gathering outside here.”

Walden police say the building is unlivable and that residents are displaced. The cause is under investigation.