Firefighters from across the region battled a massive six-alarm fire Monday on the West End, a fight that enlisted help from across the region and gave four firefighters minor injuries. The blaze erupted Monday at a 1960s-era warehouse on South Pickett Street shortly before noon, a time when the building was empty because of the Labor Day holiday.

As firefighters arrived on the scene, they were confronted with a serious and unexpected challenge. A water-main break earlier in the day left the block without water. That meant that the hydrant directly in front of the building was inoperable. So Alexandria fire officials called for help from Fairfax County, which loaned a 10,000 gallon tanker truck. That provided an immediate source of water while firefighters scanned the area for a working hydrant. Eventually, one was discovered in a nearby apartment complex. So firefighters cut through a fence and tapped off a hydrant by an apartment complex on Edsall Road.

"In emergency services, you train for not only what you expected to have there but what is unexpected," said Chief Fire Marshal Robert Rodriguez. "So if your water source is impaired, then you go to your secondary options for either alternate water mains or portable water sources in order to meet your objective."

That wasn't the only stumbling block. Just as firefighters were entering the building, part of the roof collapsed. That sent firefighters scrambling from the building and radically changed the strategy.

"We go from an offense mode to more of a defend-in-place mode," said Rodriguez. "We are going to continue to attack the fire building, but only use exterior lines as well as protect any other structures around that the fire could extend to."

ALEXANDRIA RECEIVED support from across the region to help fight the fire, including Prince George's County, Arlington County, Fairfax County and the Metropolitan Washington Airports Authority. Units from across the National Capital Region scrambled to fill in for missing units that were in Alexandria, reshuffling responders across Northern Virginia and Maryland. Assistance included help from the U.S. Navy, the Red Cross and Dominion Virginia Power. Injuries included one firefighter from Alexandria, one from Fairfax County and two from the airports authority.

"The firefighters transported to hospital from Alexandria warehouse fire were for precautionary reasons," Alexandria Fire Chief Adam Thiel announced on Twitter at 5 p.m. "Thanks for all your concern!"

At the peak of the firefight, the blaze was a six-alarm fire — meaning that six firefighting units were dispatched to help contain the blaze. By 2:30 p.m., the fire was finally contained although crews remained on the scene through the night. Tax records show the building is owned by a limited-liability corporation created by McLean-based Velsor Companies, which rents to a business known as D.C. Foam Recycle Center. Charred bits of foam could be seen littering Pickett Street the day after the fire, where the smell of smoke lingered in the air. Fire officials said the investigation will take at least a week to determine a cause.

"It's going to be a long and detailed investigation," said Rodriguez. "Investigators need to remove the roof portions that have collapsed and shore up certain areas that were damaged by the fire to ensure there isn't a further collapse. Once they make the scene safe for entry, they'll start doing a detailed investigation."