Human error is being blamed for a ruptured natural gas line that shut down Fredericton's busiest intersection for an hour on Tuesday morning.

The leak also forced the evacuation of a number of nearby buildings, including CBC's radio and television newsrooms and an Irving gas station. The Dr. Everett Chalmers Hospital, located just a block from the leak, was also put on alert and advised to shut down its ventilation system.

Firefighters with gas meters were on scene shortly after the 2.5-centimetre pipe was ruptured at the corner of Prospect and Regent streets, trying to gauge the severity of the leak.

Assistant deputy fire chief Bob Martin says a private contractor working for the city was laying lines for street lights when someone made a mistake about the location of the underground pipe.

"It was an individual — his foreman had left the site for a minute — and the individual took it upon himself, he thought he was [past the line]. It was just human error, that's all it was."

It's not the first time a gas leak has forced evacuations in Fredericton. Enbridge Gas, the supplier of natural gas throughout New Brunswick, says Fredericton has had four leaks so far in 2006.

Martin says his crews have been called to at least two other similar accidents in the past two weeks.

"We've had a few in the last couple of weeks. Again, they're small ruptures … it's human error 95 per cent of the time, it's people aren't watching what they're doing."

Martin says the private contractor's foreman should have been on the construction site while the digging was taking place. The fire department is investigating the incident.