The crash at 2:15 p.m. (1215 GMT) near the suburban Khorshid station on the route to Cairo, derailed the engine of one train and two cars of the other, the Egyptian Railway Authority said.
A railroad switching error was the most likely cause of the collision, a security source. He gave no further details.
State newspaper al-Ahram said 36 bodies had arrived at hospital morgues in Alexandria province. Public prosecutor Nabil Sadek ordered an urgent investigation, it said.
A medical official told state TV some wounded people were still stuck in the trains.
"The train I was riding was going very quickly," said passenger Moumen Youssef. "I found myself on the floor. When we came out, we found four train cars crushed and a lot of people on the ground."
In 2012, 50 people - mostly children - were killed when a train crashed into a school bus south of Cairo, further inflaming public anger at authorities over Egypt's antiquated transport network.