DENVER — A fire at an apartment construction site just east of downtown Denver grew into a massive inferno in mere moments Wednesday afternoon.

It happened at 1833 Emerson St. just after noon.

One person was killed and one other was missing. Six people needed medical treatment, including one firefighter.

One construction worker had critical injuries. The firefighter suffered minor burn injuries.

The three-alarm fire involved at least 100 Denver firefighters. There were about 50 construction workers on the site.

Some of them jumped from scaffolding to save themselves from the rapidly growing flames and intense heat.

A fire department spokesman said some of the injuries occurred from people trying to catch co-workers who jumped.

Several buildings were affected by the fire. One was destroyed and an adjoining building had fire damage.

At least six others had active fire on roofs that began because burning embers landed on them.

At least six pieces of construction equipment were destroyed.

There were at least 30 vehicles parked in alleys and the streets surrounding the fire scene that had been damaged.

The intense heat damaged three fire engines. Flames shot 200 feet into the air at one point, according to the fire spokesman.

The cause was under investigation.