It was unclear if the deceased person was on one of the buses or was a pedestrian.
Three people were killed after the buses collided - including the driver of the tour bus..
Officials said the city bus was making a right-hand turn when it was struck by the private bus, and then the private bus crashed into a restaurant, igniting a small fire inside.
Images from the scene showed the Dahlia bus crashed into a Kennedy Pizza & Chicken while the MTA bus was facing the wrong direction on eastbound Northern Boulevard.
Six people are in critical condition and 10 people are in stable condition.
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She said all four of the women, who are in their 20s, have been hospitalized, two of them for shock. The four women were studying overseas , three of them at the college's Paris program.
The National Transportation Safety Board said Monday afternoon it would be sending a team to investigate the deadly crash.
"The impact of this collision on the building was very, very substantial", said de Blasio.
"Look I'm going to let the investigation go ongoing but as we've observed these buses spun around, that requires an enormous amount of speed", he said.
"We know that one of those who was lost was simply walking down the sidewalk on Monday morning on their way to work and out of nowhere this happens", he continued.
Sources say the MTA driver pried open the doors of his bus and got his passengers off. The collision pushed the charter bus into a building wall.
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The crash is considered "very serious", and is causing "heavy traffic delays", police tweeted.
One of the company's buses was also involved in a February 2016 crash that left one person dead and 36 others.
"We're looking at all avenues", NYPD Chief Elton Mohammed said.
In February 2016, one of the company's buses rolled over en route to a CT casino, injuring 14 passengers. DNAinfo.com reported that, this year alone, federal records show Dahlia has been cited on three different occasions for speeding and failing to obey a traffic device.
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