NEW YORK (CBSNewYork) — Federal investigators say they can’t pinpoint the official cause of a deadly 2017 bus crash in Queens that killed three people.

They do, however, have an unusual theory.

(credit: NTSB)

They say a dropped thermos bottle may have gotten stuck between the brake and accelerator pedals is a possible explanation.

A metal thermos bottle was found near the pedals after the crash, the NTSB said.

WEB EXTRA: Read the NTSB’s full report (.pdf)

Three people were killed and more than a dozen others were hurt when an MTA bus and private charter bus collided in Flushing in September, 2017.

Investigators said the Dahlia Group charter bus was heading east on Northern Boulevard when it struck the Metropolitan Transportation Authority bus whose driver was trying to make a right turn onto Northern Boulevard from Main Street.

The charter bus, traveling at 60 mph, slammed right into the rear end of the city bus and spun it completely around, according to the National Transportation Safety Board.

The force of the crash sent the charter bus right through the front entrance of a fast food restaurant and cellphone store, killing charter bus driver Raymond Mong.

Police said Henry Wdowiak, 68, of Queens, was walking by on the sidewalk and was pinned and killed.

Also killed was one of the people on board the MTA Q20 bus — identified as Gregory Liljefors, 55, of Queens.

Fourteen others were hurt and had to be hospitalized in the crash.