Silver Sands State Park was closed Wednesday after a fire the night before destroyed three controversial, nearly complete buildings at the beach.

With visitors kept out, investigators from the state Fire Marshal’s Office searched the 297-acre park for what caused the buildings to catch fire at about 10:30 p.m. Tuesday.

“We’re treating it as an open investigation,” said Capt. Keith Williams of the state Department of Energy and Environmental Protection’s Environmental Conservation police.

As for whether the fire was suspicious, Williams said, “We are looking at it that way and will not rule it out.”

The nearly completed buildings were scheduled to be open for Memorial Day weekend. They are part of a contested $9.1 million construction project to create a bathhouse, concessions and office space.

DEEP Commissioner Katie Dykes said, “The park will remain closed for as long as necessary to investigate the fire and protect the safety of the public. Though we are saddened by the loss of the buildings under construction, the most important thing is that no one was injured fighting the fire.”

Jeff Beckham, a spokesman for the state’s Department of Administrative Services, which was overseeing construction, said the general contractor, Scopes Construction of New Britain, was required to carry insurance on the project. Those details are being reviewed, Beckham said.

Beckham said the structure did have temporary electrical power at the time of the fire, and that there had been no overnight surveillance.

Milford Mayor Ben Blake said investigators were working on several theories about what caused the fire, but added that he could not elaborate.

“It is a tragedy,” the mayor said, describing the project as “a big public investment.”

Some Milford residents and officials had strongly opposed the building project at Silver Sands, which annually attracts a quarter-million visitors.

Blake and other Milford city officials did not attend a ribbon-cutting ceremony for the project last December. Blake said at the time he had been unaware of the event, but he admitted there was tension over the issue.

“There are much better ways to spend $10 million, especially when the state is in dire need of funding,” Blake said in December. “Silver Sands was more of a natural type of environment. We were willing to work with the installation of a few bathrooms, but the size and scope of the plan became large.”

One of the issues — the possibility of increased roadside parking in the area — may have been defused by last summer’s initiation of the Passport to Parks program, which allows cars with Connecticut license plates to park for free at all state parks.

But, Blake said, “Overall, we still have concerns on the size, scope and need for this expansion.”

Friction between Milford and then Gov. Dannel P. Malloy reached a crescendo in 2017, when the governor overcame legislative opposition to the long-term bonding for the project, then proposed cutting education funding for 85 affluent towns, including Milford, during a summer-long budget impasse.

Milford Fire Department Battalion Chief Anthony Fabrizi said the fire was so damaging that the only thing salvageable “are the ramps and pilings.”

Fire dispatchers received 911 calls at about 10:30 p.m. Firefighters arrived to find two of the structures fully engulfed and a third building about half in flames, officials said.

“The incident was brought under control in approximately two hours,” Fabrizi said.

Twelve hours after the first reports, firefighters remained at the park, putting out hot spots. The most heavily damaged main building remained standing, but appeared in danger of collapse.

Williams said the Coast Guard and DEEP’s hazardous materials unit were notified that some particulates from the fire might have reached Long Island Sound and nearby marshes.

“The buildings were close to being finished,” Williams said. “

“It’s devastating for the Department of Energy and Environmental Protection to put this kind of effort into a project like this and see it go up in flames in a short amount of time, especially when it was projected to be open for Memorial Day weekend for the public to utilize,” Williams said. “So it’s definitely a setback for us, for the agency.”

DEEP said officials from the Department of Administrative Services, which oversees the construction, have begun coordinating meetings with the project contractor to determine the next steps, and that Milford officials “have reached out to DEEP to offer their support and coordination.”

Before the project was approved, state Rep. Kim Rose, D-Milford, had proposed a bill to reduce its scope. Rose said she didn’t oppose all aspects of the Silver Sands project, such as the restrooms. But she had concerns about a storage facility and office space for DEEP employees.

In a written commentary about her proposed bill, Rose said, “It’s difficult for others who either do not live in Milford or go to Silver Sands to understand that this is an environmental issue, a pristine natural area that should remain that way. Bonding this much money is irresponsible for a project that is a luxury.”

Rose was at the state park Wednesday morning and said the fire was a shame but that she was grateful no one was hurt.

“Yes, we opposed it,” Rose said as she looked at the destruction caused by the fire, “but it was built, and no one likes to see this happen.”

Staff writer Jill Dion contributed to this report.