A body believed to be that of a young woman who went missing after a personal watercraft collision Sunday night has been recovered from the Merrimack River, according to Middlesex County District Attorney Marian Ryan.

The search for the 16-year-old girl was concluded Monday morning after hours of searching. The girl went missing Sunday night after two personal watercraft collided and a search was immediately launched.

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The Chelmsford fire chief told the Lowell Sun that they received a 911 call around 10 p.m. Sunday from a person who said two personal watercrafts had collided on the river, throwing the girl into the water.

According to Ryan, the 16-year-old girl was a passenger on a personal watercraft. She said the operator was also thrown into the water, but made it back to shore.

"We brought all of our resources to bear here," Chelmsford Police Chief James Spinney said.

Chelmsford search and rescue boats were assisted by Lowell and Tyngsboro crews, who searched both banks of the river Sunday night.

A man has been arrested in connection to the crash, according to police.

Douglas Dematos, who was in the hospital recovering from injuries Monday morning, was charged with operating a personal watercraft under the influence, operating at night, operating recklessly, operating too close to another vessel and without a light.

"This is not a waterway that is meant to be used during the evening," Ryan said. "There is a restriction to not be out here once darkness falls."

Dematos, 31, from Lowell was held in the hospital overnight, police said. Officers added that the people who were on the personal watercraft Sunday evening were all in a group together and know each other.

"(Personal watercraft) should absolutely not be operated at night," Chelmsford police Chief James Spinney said. "This equipment cannot be operated when your brain is in an impaired state and they'll have to answer to that."