Photo: The Canadian Press

Firefighters responding to a call about a gas leak in Portland, Oregon, saved lives when they ordered evacuations and pulled a fire alarm to warn holdouts just minutes before a powerful explosion levelled a historic building in a popular shopping district, officials said.

The blast injured eight people Wednesday morning and ignited a fire that sent a plume of smoke over the city. Three firefighters, two police officers and three civilians were hurt.

The firefighter with the most serious injury, Lt. Peter St. John, was in good spirits following surgery for a broken leg, Portland Fire & Rescue Lt. Rich Chatman said Thursday.

He and other firefighters and police helped avert a catastrophe by quickly clearing the area before the explosion, city officials said.

"There are a lot of people alive" who might not be "but for the excellent work by our first responders," Mayor Charlie Hales said.

In particular, St. John made several critical decisions that likely saved lives, Portland Fire Chief Mike Myers said. He positioned the fire trucks in such a way that they were out of the blast zone and then ran into the building to pull fire alarms when firefighters realized everyone had not evacuated, Myers said.

St. John and other firefighters also decided to don protective equipment before the blast because something "just didn't feel right," the fire chief said.

"That man saved the lives of a lot of people today and a lot of firefighters," Myers said. "He had very good instincts today. He showed good judgment."

Police officials also credited two officers who were recovering from "concussive-type" injuries at home.

"I'm told they had to be basically pulled from here to go to the hospital," police Sgt. Pete Simpson said. "They did not want to leave their post. They were here to help out and do whatever they could."

The blast reduced to rubble a 110-year-old building that housed a bagel shop and other businesses in the popular NW 23rd Street shopping district.

The walls and windows of a nearby building were blown out and businesses three blocks away reported that their doors flew open from the force of the blast. The intersections near the blast site were still closed Thursday.

Construction workers nicked a three-quarter-inch natural gas line outside the building and gas collected inside, Chatman said. The ignition source has yet to be determined.