The Q train derailment that disrupted service for about eight hours last Friday was the result of improper maintenance of a subway car, according to Wynton Habersham, the head of New York City Transit’s subways department.

Speaking at the MTA’s monthly Transit Committee meeting Monday morning, Habersham said that although the derailment is still under investigation it appears that a "failure to follow proper maintenance procedures" caused an “abnormal condition on a truck” of the derailed car, particularly on its wheel and axle.

"We sincerely apologize to our customers,” Habersham said. “We know we need to improve.”

Habersham said the MTA is inspecting all of the trucks and axles of that train car model, known as the R160. The agency is "about 70 percent" through that inspection, he added.

The Coney Island-bound Q train carrying 135 passengers derailed at the Brighton Beach station in Brooklyn around 8:58 a.m. on Friday, according to officials. 

No injuries were reported after the incident and all passengers were evacuated safely from the train, but the derailment snarled service on the B and Q lines until just after 5 p.m. on Friday.

John Samuelsen, president of TWU International and TWU Local 100 representing subway workers, said the MTA cut back on equipment inspections and maintenance years ago, and now riders are feeling the effects.

"There is a direct correlation. The system needs more workers, more boots on the ground, so subway cars and signal are checked and maintained much more frequently," Samuelsen said in an emailed statement following Habersham's comments Monday. 

The incident was just the latest in a string of service disruptions plaguing the subway system. 

Earlier in July, a track fire caused by trash near the 145th Street station in Harlem caused service disruptions and overcrowding on several subway lines. And an A train derailment in June injured at least 39 people. The cause of that derailment was later determined to be due to human error after a piece of scrap rail was improperly stored on the track, officials said.

The MTA's subway system is a state-run agency led by Gov. Andrew Cuomo, but the governor has been attempting to shift some of that responsibility to Mayor Bill de Blasio in recent days, suggesting that the city needs to contribute more funding to improve the aging infrastructure.

De Blasio fired back at Cuomo during a news conference on board a Brooklyn-bound F train Sunday, calling the governor's assertions "fiction" and reiterating that the MTA and the state are responsible for operating the subway.