KITTERY — Divers on Wednesday discovered damage to an underwater pier that supports the Sarah Mildred Long Bridge after a 470-foot tanker broke from its moorings Monday and drifted into the bridge.

Engineers have yet to release an estimate on the cost of fixing the 73-year-old span, said Bill Boynton, spokesman for the New Hampshire Department of Transportation. He said the bridge would remain closed for two to four weeks to vehicle traffic; river traffic has resumed.

The damaged granite was found on the southernmost of two underwater piers, Boynton said. Two steel trusses that were bent by the impact also must be replaced. Engineers still are examining the impact area, he said, and a private contractor is close to signing a deal to perform the repair work.

“The bridge took a big hit,” said Ted Talbot, spokesman for the Maine Department of Transportation, who released a cost estimate of about $500,000 early Wednesday but withdrew that estimate later in the day. “There’s a lot of different scenarios taking place at this point.”

Both Maine and New Hampshire own the bridge, although New Hampshire operates its lift span, which gives access to the Piscataqua River and harbor.

The tanker, called the Harbour Feature, also was damaged in the crash. The impact cracked the ship’s skin, allowing water to leak into a ballast tank used to stabilize the vessel when it is empty.

At the time of the impact, the MS Harbour Feature was carrying tallow, made from wood pulp oil, and yellow grease. No substances have spilled into the waterway. Steffen Thate, a spokesman for TB Marine Shipmanagement in Hamburg, the company responsible for the ship’s management, said the company is working with U.S. authorities to determine what caused the tanker to come loose from its moorings.

“We are investigating the unfortunate accident and cooperate fully with all state and federal government agencies,” Thate wrote in an email.

Workers and business owners in Kittery were largely indifferent to the closure of the bridge, which carries about 14,000 vehicles per day. Only one of the three bridges connecting Kittery to Portsmouth is operational now.

The tanker accident is the latest transportation glitch for the Kittery and Portsmouth communities. Earlier this year, the lift span of the Long bridge was stuck open, snarling marine traffic.

Coupled with the closure in July 2011 of the nearby Memorial Bridge, residents traveling between the states must traverse the busier I-95 bridge, which carries about 112,000 vehicles per day.

At Jackson’s True Value Hardware and Marine in Kittery, near the foot of the Long bridge, Joe Calderara was less than excited about the suddenly barren stretch of the four-lane U.S. Route 1 bypass that runs in front of the store.

Half of the store’s customers live in New Hampshire, Calderara estimated.

“It’s going to hurt us, but in the long run we’ll win the fight,” he said.

Customers of Island Marine Service on Route 236 also are likely to suffer from the closure, said John Morrell, a technician who was refueling a dinghy at a busy gas station near the bridge.

“For us it’s no biggie, but for the customers it’s a different story,” Morrell said.

Jeffrey Pelkey, who operates a funeral home close to the damaged bridge, said his customers will have a tougher time reaching his business.

Pelkey, who also chairs the board of the Greater York Region Chamber of Commerce, said the closure illustrates the need for states to manage infrastructure improvements better.

The Sarah Mildred Long Bridge was at the top of New Hampshire’s list of aging bridges that need to be replaced or repaired, according to Boynton, the transportation spokesman.

“It speaks to a bigger picture of proper planning, that both these bridges were in such bad shape,” Pelkey said. “It’s a tough lesson for us to learn.”