BEVERLY - Two off-duty Beverly police officers on their way to the gym yesterday got their adrenaline pumping early, running into a three-story apartment building with smoke billowing from the eaves. Once inside, they started banging on doors and kicking some of them down, as they evacuated almost a dozen residents.

The two longtime cops helped get everyone inside the five occupied Gloucester Crossing apartments out of the building before firefighters began hours of work to knock down a three-alarm fire.

No one was injured in the blaze, which started at 12:45 p.m.

"Both of us needed to break down the door to get in," said police Lt. Mike Sungy, describing what he and Patrolman Donald Call did after opening the single unoccupied apartment on the third floor and seeing flames coming from a ceiling fan.

The building has two apartments on each floor. Sungy and Call started banging on the door across the hall and worked to knock it down.

"There were three or four or five people in that apartment. I don't know if they were frightened because we were yelling 'fire,' yelling 'police,'" Sungy said. "They were oblivious to everything. They had no idea the place was on fire."

Sungy and Call checked the remaining apartments and found occupants on the second and first floor, as well.

Sungy said he didn't hear any fire alarms going off in the apartment building at 390 Cabot St., near the MBTA commuter rail tracks at one of the busiest intersections in the city.

Sungy and Call, both with 20 years with the Beverly Police Department, were driving to the gym at the Cummings Center when they saw smoke coming from the building's eaves. They pulled over in front of the 7-Eleven across the street and ran into the burning building.

"Funny thing was, there were people everywhere (outside), but everyone seemed to be oblivious as to what was happening," Sungy said.

The fire displaced five families, a total of about 20 people, many of whom had moved in only recently.

The family on the third floor that was first to be evacuated had moved into their apartment last weekend; the U-Haul truck they rented was still parked in the driveway in the rear.

In November, Rebecca Ruest moved into her second-floor apartment with her two sons and their two cats. Firefighters rescued Bruin - "He's hard to miss," Ruest said - but there was no sign of Valentine, a cat she got last February.

"I still have my cat in there," she said with tears running down her cheeks as she watched her home burn. Family members draped a Red Sox blanket over her shoulders as she waited. Twenty minutes later, she was cradling Valentine - who was OK - in her arms. Firefighters also saved a couple of hamsters from a first-floor apartment.

Yet there were losses.

Many families still had Christmas presents sitting under the tree, and Russell Bogrett had just bought brand-new furniture for his entire second-floor apartment, as well as a computer. But what really mattered to him was the "sentimental stuff." Old World War II memorabilia, family pictures, and china and crystal that his parents received as wedding presents in 1942 were all priceless.

"I'm just hoping I can get that stuff out," he said.

In June, the apartment building was sold to a new landlord for $300,000. Bogrett, who has lived on the second floor for the past four years, said there had recently been a lot of renovations to the third floor, including electrical work.

A large "For Rent" sign was plastered to the front of the building with a phone number, but no one at that number returned a call yesterday.

Beverly fire Capt. Peter O'Connor said most of the damage occurred on the third floor. Firefighters started the attack by spraying from the inside, and about an hour into it the blaze seemed to be dying down. But then all firefighters were ordered out of the building: The fire was spreading through the cockloft - the space between the ceiling and the roof - damaging the structure holding up the roof. It eventually collapsed.

"The guys were inside making very good progress, but the fire made its way to the back of the building and through the roof," O'Connor said. Oxygen from the outside drove the flames higher.

"In a matter of two minutes, it went from looking good to the fire gaining control," O'Connor said.

Local firefighters were joined at the scene by squads from Danvers, Salem, Hamilton, Wenham, Manchester, Topsfield, Middleton and Swampscott. Marblehead, Peabody and Ipswich departments provided station coverage.

They changed their strategy to hosing down the outside of the building and by 4 p.m. it was nearly out. Fire investigators were at the scene of the fire until late last night.

O'Connor said the cause of the fire is still under investigation.

The local chapter of the American Red Cross made sure all the families had a place to spend the night and is working to help them secure temporary residences, as well as providing financial assistance for rent and items lost like clothes, toiletries and linens.

The damage to the apartment building is still being assessed.