A community is in mourning after three teenagers were killed in a house fire in Whitby over the weekend.

The fire occurred early Sunday morning on Dundas Street in Whitby, and killed three people in the upstairs unit of a house that was divided up into several units.

On of the victims has been identified as Ben Twiddy, 19, a Grade 12 student at Anderson Collegiate.

The two young women killed in the fire have been identified as Hollie Towie, 17, and Holly Harrison, 18.

One of the victims managed to call 911 at 12:25 a.m. on Sunday morning, police said. Firefighters arrived minutes later, but the smoke was so bad that they could not get the teens out of the house.

"We do know that, where they were located, that there was fire between where they were located and the entrance," said Whitby Fire Chief Michael Gerrard.

By Monday afternoon, a memorial of flowers had sprouted on the lawn in front of the house.

"It doesn't really seem real, almost," said one teen who laid flowers. "You hear about it happening in other places and to other people, but you never think it's going to happen to people who you see every day."

Flags were lowed to half mast at three Durham district schools to mourn the students.

Karen Allan, principal at Anderson Collegiate where Twiddy was a student, said grief counsellors were being made available to the students.

"Obviously, they are devastated right now," said Allen. "So, we just need to help them talk it out and to remember the fond memories to deal with this tragic event."

Investigators are still trying to determine what caused the blaze, but they say it is not considered suspicious. They are looking into whether the house had working smoke alarms and a proper escape route.

With files from CTV Toronto's Ashley Rowe