Another rail broke on the F line in Queens, just days after a derailment Friday injured 19 riders and stranded over 1000 people, authorities said.

A special track car with a computer was scanning the rails during routine maintenance work when it found a crack shortly after 3 a.m. near 36th Street in Long Island City, an MTA spokeswoman said.

The car does ultrasonic testing of the rails during maintenance work.

An inspector then looked at the broken rail, and repairs began until about 6:45 a.m.

The F train ran local during that period.

A broken rail caused the frightening derailment on the F line near 65th street Friday.

The cause of the break in the rail, which had been recently installed, is still under investigation.