BOSTON -- A 200-pound manhole cover crashed through a windshield on a major Boston highway during the morning commute Friday, killing a driver, Massachusetts State Police said.

A manhole missing its cover on I-93 south near the exit of the O'Neill Tunnel. CBS Boston

Authorities said the metal manhole cover became "dislodged and airborne" before it slammed into a car in one of the southbound lanes just before 8 a.m., CBS Boston reported.

State Police spokesman Dave Procopio said in statement that the manhole cover came loose at about 7:50 a.m. and that the vehicle it hit continued forward before striking a wall on the left shoulder of the highway and coming to a stop.

Caitlin Clavette CBS Boston

The driver was later identified as Caitlin Clavette, an art teacher at an elementary school in Milton, CBS Boston reported.

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School district officials said Clavette had taught art for the past four years at Glover Elementary School, describing her as gifted and talented. Counselors will be on hand at the school Saturday.

Friends told CBS Boston the 35-year-old was a triathlete who simply loved life.

"She was a laugh a minute," Sherman Roberts said. "This woman was just a good spirit. I mean, there's no words to describe how nice and kind she was."

"It's just an awful shame and it will take me a while to really comprehend it and life is unfair and this is just one of the worst things that can happen to such an amazing person," said friend Mike Nislick.

A manhole cover rests on the highway after it smashed into a car Friday. CBS Boston

It's unclear what caused the manhole cover, normally situated in the left southbound lane near the exit of the O'Neill Tunnel on I-93 South, to become dislodged. That is part of an ongoing investigation, Procopio said.

Two lanes of the highway were shut down while the investigation was underway Friday.

Following the crash, Massachusetts Department of Transportation crews and welders spent the afternoon examining all travel lane infrastructure in Boston to check that manhole covers, grates, and covers for electrical panels were secure, according to CBS Boston.

"The equipment involved in the incident covers a storm drainage system and was last inspected June 12, 2014, and there is no indication the manhole has been removed recently for any necessary work," MassDOT Administrator Thomas Tinlin said in a statement Friday afternoon.