PORTLAND — The Falmouth couple accused of hosting an end-of-the year party where minors drank alcohol and smoked marijuana have entered not guilty pleas in the case.

Barry and Paula Spencer had an arraignment scheduled for Thursday in Cumberland County Unified Criminal Court. Each of their lawyers entered their not guilty pleas by letter in advance so they were not required to be present.

The husband and wife have each been charged with nine counts of allowing a minor to possess or consume alcohol. If they’re found guilty, the law prohibiting adults from furnishing a place for minors to drink requires a mandatory $1,000 fine for each conviction.

The pair was indicted last month in connection with a June 16 party at their home. Their lawyers have said that the party started as a small gathering but grew to nearly 100 people as students, some from other towns, joined it.

Police said no responsible homeowner could have been unaware of what was taking place.

Falmouth High School had won Class B state championships in baseball and lacrosse that Saturday — the day after school ended for the year — and members of those teams were among the teenagers who gathered, police said.

Police say 75 to 100 high school students were at the house at 35 Fieldstone Drive, and 35 to 40 cars.

The initial summons that police issued to the Spencers did not lead to a complaint by prosecutors, according to Walter McKee, Barry Spencer’s attorney. However, the case was presented to a grand jury.

Grand jury proceedings are secret and so it is unclear whether prosecutors compelled testimony from minors who were at the party in order to obtain more evidence to support charges.

Police say they initially got a tip about underage drinking at the party, but when they went to check at 10:30 p.m., they were told by Barry Spencer that there was no drinking.

An hour later, police stopped a car with teenage passengers who said they had been drinking at the Spencers’ home.

Four officers went to the home and found minors drinking and smoking marijuana, police said. They said they found one teenager passed out on a nearby lawn and vomit on one of the cars.

A 17-year-old girl was charged with administrative drunken driving, meaning her blood alcohol content was less than 0.08 percent, but because she is younger than 21 she is not allowed to drive with any alcohol in her system.

Two other teenagers were charged with possession of alcohol, and another was charged with possession of marijuana. Three were charged with possession of alcohol by consumption.