Just how much is 17½ tons of cocaine?

Enough to fill 15,582 plastic-wrapped bricks. Enough when laid out end to end, officials said, to span 2½ miles — from Old City to the Art Museum.

And so much that on Friday, as federal authorities unveiled the results of this week’s seizure at the Port of Philadelphia — one of the largest drug busts in the nation’s history — only one-fourth of their total haul could be crammed into the U.S. Custom House lobby.

Although reports earlier put the total at 16½ tons seized, additional searches yielded another ton, for a total estimated value of $1.1 billion.

“Thirty-five thousand pounds of cocaine is an incredible amount,” said Casey Durst, director of field operations for the regional office of U.S. Customs and Border Protection. “A street value of over a billion dollars is hard to conceptualize. Really, it’s just incredible.”

Friday’s news conference was big on splashy visuals, but less so on any new information.

Representatives from a half-dozen state, local, and federal agencies stood shoulder to shoulder, flanked by an eye-popping amount of cocaine wrapped in cellophane, stacked on wooden pallets, and stuffed into evidence boxes. White House drug czar Jim Carroll offered congratulations directly from President Donald Trump, while armed agents wearing bulletproof vests kept an eye from a balcony on the contraband and a crowd of reporters.

But officials demurred from saying what had led them to the MSC Gayane, the international cargo freighter on which they made their record-breaking discovery Monday.

Asked several times, they cited routine port inspections, and made vague references to intelligence partners.

“What we do investigatively is part of our trade craft, so I can’t go into that,” said Marlon Miller, special agent in charge of the Philadelphia branch of Homeland Security Investigations.

Authorities also remained circumspect about the roles of the six members of the ship’s crew whom they have placed under arrest.

“This investigation is ongoing,” U.S. Attorney William M. McSwain said. “The situation is very fluid.”

He added that his office was considering all possible civil and criminal penalties, including a possible attempt to seize the Gayane — a freighter the length of three football fields — in criminal forfeiture proceedings.

Agents intercepted the vessel in mid-voyage Sunday night and directed it into the Packer Avenue Marine Terminal, Durst said. They spent Monday, Tuesday, and much of Wednesday scouring the ship with fiber optic scopes, drug-sniffing dogs, and an X-ray scanning truck.

Authorities said the cocaine had been hidden in seven shipping containers and stashed among wine, vegetable extract, Chilean dried nuts, and scrap metal from the United Arab Emirates, and other legitimate cargo bound for destinations in Europe, Africa, and Asia.

Investigators said Friday it was too early to say where and when the drugs were brought aboard the ship or their intended destination. Before it was impounded in Philadelphia, it was scheduled to head to France and the Netherlands.

In court filings that have since been sealed, two members of the crew — Ivan Durasevic, 29, the Gayane’s second mate, and seaman Fonofaavae Tiasaga, 28 — confessed to helping smuggle the cocaine aboard in exchange for payments of 50,000 euros.

They described men wearing ski masks hauling nets filled with thousands of white-powder bricks from 14 boats that separately approached the Gayane this month as it journeyed between Peru and Panama.

Both Durasevic and Tiasaga implicated unnamed crew members, the court filings say. But officials would not say Friday whether any of the others facing charges were among those singled out by Durasevic or Tiasaga.

The other four men in federal custody are Lauuli Pulu, 32, an ethnic Samoan, and Montenegrins Bosco Marcovic, 37; Aleksandar Kavaja, 25; and Nenad Ilic, 39.

All six are accused of violating federal maritime drug smuggling laws and could face up to life imprisonment if convicted.

Their attorneys declined to comment pending a court hearing Monday afternoon.

Meanwhile, the Gayane and its remaining crew are stuck in the United States as agents continue to investigate. Its illicit cargo will be incinerated once it is no longer needed as evidence, officials said.

A spokesperson for Mediterranean Shipping Co., the Swiss-based firm that owns the cargo ship, did not return phone calls Friday.