Dow Chemical sent a fuel truck from Bristol, Bucks County, to help volunteer units that were running low, and Camden sent a fireboat to assist that drew water from the Delaware River.
Crews from several other counties came to help as well, including Gloucester, Mercer, and Ocean in New Jersey and Montgomery in Pennsylvania.
No injuries were reported Sunday night. According to the Associated Press, the only people on the company grounds when the blaze erupted were two security guards staffing a station outside the building.
The fire remains under investigation.
The 266,000-square-foot plant was closed for the Labor Day holiday weekend, according to Delanco Police Chief Jesse DeSanto.
The plant, which received a $175,000 state income tax break, was built for $20 million. It houses Dietz & Watson's Black Bear distribution arm and employs more than 100 of the company's nearly 1,000 workers.
Dietz & Watson, a 74-year-old Philadelphia company, sends hams, salami, and other beef and pork cold cuts from its Bridesburg plant; chicken and turkey from its Baltimore works; and cheeses from its Corfu, N.Y., plant to the Delanco distribution center, said Steve Riley, spokesman for the company.
The firm is run by descendants of founder Gottlieb Dietz.
The Delanco facility then trucks the cold cuts to grocers, hoagie shops, and other retailers.
Riley said each plant had a supply of the company's newly made products ready to ship, and the company expected to keep filling orders.
"This is a tough Labor Day weekend for the Dietz & Watson family, but we are relieved all of our employees are safe," chief executive Louis Eni said in a statement.
He called the Delanco facility a "state-of-the-art distribution center" that ships to clients around the world.
"It will take more than a fire to set us back," he said.
"We are so grateful to the brave firefighters who are working to put out the fire."
Contact Joseph N. DiStefano at 215-854-5194, JoeD@phillynews.com, or follow @PhillyJoeD.
Inquirer staff writer Ben Finley contributed to this article.