CARLISLE — Looking to hit the spot with a savory ice cream at Great Brook Farm State Park this week?

You may be out of luck.

The park’s popular ice-cream stand was unexpectedly shut down by state officials over the weekend, after the stand’s operator made building improvements at the site without getting permission first.

Mark Duffy, who has operated the dairy farm at the state-owned park for 26 years and has a lease with the state to run the stand, said armed Environmental Police officers showed up at stand on Friday evening and stood guard throughout the weekend, turning away customers craving delectable sundaes and frappes.

To make matters worse, said Duffy, the shutdown happened right before the sunny Mother’s Day weekend.

Edward Lambert, commissioner of the Department of Conservation and Recreation, said the stand was closed after it was discovered construction had been done without local or state permits. The work, which expanded the stand, included construction on a barn built in 1910 that is adjacent to the stand, he said.

Lambert said he is trying to protect the public’s health and safety while tests are conducted at the site.

“I like ice cream as much as anybody, so it pains us to even temporarily close what is an iconic property, but we have to make sure people eating ice cream there are safe,” said Lambert.

Duffy said he has made countless improvements to the farm over the years without permission.

“The reason I’m here and the purpose of having me here is to improve the facility and operate a commercial dairy farm,” said Duffy, 57, who lives on the farm with his wife. “I make improvements every single day and have for 26 years.”

Calls to George Mansfield, the administrator of the Carlisle Planning Board, were not returned regarding local permits.

Lambert said it is not known when the stand will reopen.

There are 13 high-school and college students who work at the stand who are now without jobs, said Duffy. While there are 140 milk-producing cows at the farm, the ice cream is shipped in from Bliss Bros. Dairy, an ice-cream manufacturer and distributor in Attleboro.

Duffy offers guided barn tours at the farm from May to October. The building improvements in question were made to create an area to show an instructional video produced by the Massachusetts dairy industry, said Duffy.

The 1,000-acre park is located in Carlisle and Chelmsford. In addition to the dairy farm, there are more than 20 miles of trails available for walkers, hikers, mountain bikers and horseback riders. During the winter, trails are open for cross-country skiing.

Duffy also operates a 40-acre cranberry bog that produces up to 100,000 pounds of cranberries annually. He sells composted cow manure and grows corn and grass, as well.

But without revenue from the ice-cream stand, Duffy said operating the farm could be financially perilous.

“On a diversified farm like this, the only way to stay in business is to make all the pieces work together,” said Duffy. “I have expenses. I just don’t have that income anymore. It’s a seasonal business, but this was done on Friday at 6 p.m. on a beautiful Mother’s Day weekend.”

Follow Chris Camire on Twitter at camirereports.