When a deluge of water poured into the Queens-Midtown Tunnel earlier this month, MTA crews spent hours trying to figure out the source of the leak that forced officials to temporarily close the busy crossing.

The case was finally cracked when a brave MTA worker tasted the mysterious liquid pouring into the tube, transit officials said on Wednesday. The worker found the water was salty, which meant it was coming in from the East River and not from a burst water main.

“How we determined it was salt?” MTA Bridges and Tunnels President Cathy Sheridan said during a news conference. “Yes, someone did taste it.”

“Yum, yum,” MTA Chair Janno Lieber responded.

MTA officials reported the leak around 10 a.m. on Sept. 4 — but about two hours passed before the worker put their palate to use to discover the water’s briny notes, according to a timeline of the incident shared by the agency. The MTA initially reported the leak was caused by a broken water main, which would have spilled fresh water. But the East River’s water is salty, because it’s not a river at all, but a mighty tidal estuary that flows between New York Harbor and the Long Island Sound.

The salty flavor led MTA crews to investigate a barge set on the waterway above the tunnel, where a construction company was drilling as part of a project to expand Manhattan’s East Side greenway. Officials closed the crossing, which is used by about 90,000 drivers daily, out of fears that the company’s drill compromised the tunnel’s structural integrity.

MTA workers dispatched crews to make temporary repairs, and fully reopened the tunnel by 5:37 p.m., officials said. City officials said the workers who caused the leak drilled 50 feet beneath the riverbed, deep enough to snag the tunnel.

Transit officials said they did not determine how much water ultimately flowed into the tunnel, but Lieber said “there was never more water than the tunnel’s normal drainage system could accommodate.”