BOSTON (CBS) – A Milton art teacher was struck and killed by a flying 200-pound manhole cover on Interstate 93 in downtown Boston during rush hour Friday morning.

It happened just before 8:00 a.m. as Caitlin Clavette was driving southbound through the O’Neill Tunnel. She suffered fatal injuries when the metal disc crashed through her windshield.

“The cover normally rests atop a manhole in the left lane of Route 93 southbound near the exit of the O’Neill Tunnel,” State Police spokesman Dave Procopio said in a statement.

“Preliminary investigation suggests it struck the victim’s windshield somewhere in that vicinity. After impact, the vehicle continued southbound in the left lane of Route 93 reaching near the area of East Berkeley street before hitting the wall on the left shoulder and coming to a stop.”

“What caused the manhole to become dislodged is part of the ongoing investigation,” Procopio said.

Two lanes were blocked for several hours following the accident, causing delays.

Terry Granahan of Hingham drove by just after it happened and couldn’t believe it.

“It’s devastating. You’re driving and something falls on your car and kills you. It’s just absolutely devastating. It’s tragic,” he told WBZ NewsRadio 1030.

The metal cover that flipped into car windshield, killing expressway driver says "Boston Drain" on it. #wbz pic.twitter.com/lX2puBh0qU — Christina Hager (@HagerWBZ) February 12, 2016

“Our sympathy goes out to the family of the victim involved in this horrific incident this morning. This tragedy is leading us to take several steps immediately out of an abundance of caution,” MassDOT Administrator Thomas Tinlin said in a statement Friday afternoon.

Tinlin said MassDOT crews and welders will examine all travel lane highway infrastructure in Boston Friday to make sure manhole covers, grates, and covers for electrical panels are secure.

Several lanes were shut down for the inspections of what Tinlin said are “more than 500 pieces of hardware on the roadway” in the city.

“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,” Tinlin said.

WBZ NewsRadio 1030’s Carl Stevens reports

