This is a la "The Great Escape" with a 50 yard tunnel dug by prisoners.
But other details open the door to questions about whether this was an "escape" or something else. The Washington Post:
They attacked a guard with daggers, snatched his gun and fired it as they were making their escape, the official told The Washington Post. One guard was fatally shot, and another was wounded.
The Associated Press reported that bands of gunmen attacked the prison from the outside just as the prisoners were escaping, opening fire on guards to divert their attention from the escape.
The official told The Post that 57 of the 62 escaped militants had been convicted on terrorism charges, and some had been sentenced to death. Twelve of them were from a particularly dangerous al-Qaeda cell known as the Tarim cell, the official said.
Pretty darn good coordination, I'd say. And this was supposed to be a high security prison? Guards didn't notice the inmates carting a couple of tons of dirt away? Didn't inspect to see if there was tunneling? Didn't search the cells for daggers?
This was either the most incompetently run high security prison around or perhaps there were some guards and even prison officials who didn't mind so much if 60 terrorists escaped.
In Yemen these days, anything is possible.