Fire crews battled a huge blaze at a building under construction in Calgary's Beltline area on Saturday morning and were able to keep it from spreading.

The fire broke out at about 11:45 a.m. at a building located at 103 17th Avenue S.E.

“A passerby noticed flames and smoke coming from this building under construction on 17th Avenue and Centre Street in the south and even before fire crews arrived it was very obvious that this was going to be a fairly large fire,” said Carol Henke from the Calgary Fire Department.

Monty Murray and his wife were in the area when the fire started.

“There was one explosion, probably a propane tank going up,” said Murray. “Unbelievable. You could feel the heat from here and everybody got moved back.”

Aerial units were brought in to fight the fire from above and get in under control.

Officials say no one was injured in the fire and a residential building beside the structure was evacuated as a safety precaution.

“We have no reports that anyone was inside the building at the time of the fire. We can’t confirm that but that’s what we are to understand and no injuries have been reported up until this point,” said Henke. "The smoke, very toxic and there is debris landing as far as four or five blocks away so anyone in the vicinity, just keep an eye open."

Police put up barriers in the area to allow crews room to work and shut down 17th Avenue between 1 Street SW and Macleod Trail SE.

“Because it’s a building under construction, there are openings, there’s a lot of wood and the fire grows very, very quickly and is quite dramatic to see. The flames were visible from probably a kilometre away,” said Henke.

18th Avenue from 1 Street SW to 1 Street SE is also closed to traffic and officials say the closures will remain in effect overnight.

"I think it's really important for people to avoid this area because traffic is backed up around and we've got multiple blocks closed off by CPS and we have other agencies on scene as well," said Henke.

The site used to be home to the Shaarey Tzedec Synogogue, which was bulldozed in 2013 to make room for the new condo development.

Torode Realty was in the process of developing the mixed-use site and construction on the 48-suite, 929 square metre building was scheduled to be complete by June 2015.

Crews will now need to determine if the building will have to be knocked down and investigators are looking into a cause.