PHILADELPHIA (CBS) — The first-ever direct flight from Philadelphia to Iceland made an unexpected stop in Boston, early Wednesday morning.

Iceland Air Flight 828 was grounded because of technical problems.

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An Iceland Air spokesperson says flight attendants and passengers in the rear of the plane smelled a “light odor,” likening it to the scent of rubber.

“My friend and I had the seats in the back row,” said passenger Brett Slakoff. “The problem seemed to have been coming from the back of the plane and there was a weird smell when we got onto the plane. I just equated it to the bathroom.”

Pilots checked it out —  and over Canada, only about two-and-a-half hours into the flight, they decided to turn the plane around and have the problem checked by safety inspectors.

Meantime, passengers were left wondering exactly what went wrong.

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“There wasn’t anything particularly weird about the plane, it was maybe a little bit hot so I wasn’t sure if there was an air conditioning issue,” said passenger Melissa Ostroff. “Otherwise, it was a very normal, relaxing flight until that happened.”

Passengers were given hotel vouchers at Logan International Airport in Boston until the plane is fully checked out and given the all clear.

On board the failed flight was Philly Mayor Jim Kenney.  His office says he’s staying the night in Boston like the others.

The pasengers are expected to leave Boston by 4:30 p.m. Wednesday.

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The plane was on its way to Iceland’s capital, Reykjavik.