The AFP news agency reports that the head of Iran's state-owned railway company has resigned following a train collision that killed at least 44 people and injured dozens.
The November 25 collision in the northern province of Semnan was one of Iran's worst rail disasters ever.
A provincial prosecutor said a train driver and three people in charge of a control center based in the city of Shahroud have been arrested.
AFP reported that Iranian Railways chief Mohsen Poor-Seyed Aghaie appeared on state television late on November 26 and said he was resigning "as a social responsibility and out of sympathy for the survivors of this accident."
Aghaie blamed the collision on "human error."
According to AFP, he said an official at the control center had told the driver of one of the trains to manually disable an automated system that was preventing it from moving toward the second train, which was stopped on the tracks after an apparent mechanical failure.
The report said that Aghaie is also a deputy transport minister.