AUBURN — A gas leak prompted emergency workers to evacuate the Auburn Mall Tuesday morning.

An excavator operated by a local contractor ruptured the 2-inch gas line that’s made of hard plastic and is pressurized at 55 pounds per square inch, Deputy Auburn Fire Chief Michael Minkowsky said. Because natural gas is lighter than air, it rose into the sky and dissipated, he said.

As a precaution, authorities evacuated buildings within a 300-yard radius, he said.

Firefighters stood by dousing the leak in an effort to help the gas dissipate and also to be ready had the gas ignited. There was no shutoff valve locally, so utility workers had to dig a hole down to the line about 50 feet upstream from the leak and clamp off the pipe behind the mall along Turner Street, Minkowsky said.

From the time of the call until the time it was shut off was about an hour and 20 minutes, he said.

Although the gas line was marked by Dig Safe before excavation started, the excavator apparently dug too deep, nicking the line, Minkowsky said. Crews had been working in the area to reroute the gas line.

During the leak, utility workers and firefighters checked the mall area for gas levels. Mall officials shut off intake vents to the mall air system, he said.

The mall was reopened before noon, Minkowsky said. The leak was similar to another rupture about a month ago on Center Street, he said.

“Another potential tragedy averted,” he said.

An Auburn firefighter sprays a stream of water in preperation for a crew from Unitil, formerly Northern Utilities, to use the orange backhoe, center, to dig around a gas pipe to clamp is shut. At right is an excavator that hit the natural gas pipe going into the Auburn Mall while working in the parking lot adjacent to Turner Street in Auburn Tuesday morning.

A crew from Unitil, formerly Northern Utilities, works to clamp shut a natural gas pipeline on the South side of the Auburn Mall Tuesday morning. A crew from K&K Excavation was working in the parking lot when their excavator, right, hit the line and created the leak which closed the mall and other area businesses and roads.

A crew from Unitil, formerly Northern Utilities, works to clamp shut a natural gas pipeline on the South side of the Auburn Mall Tuesday morning. A crew from K&K Excavation was working in the parking lot when their excavator, right, hit the line and created the leak which closed the mall and other area businesses and roads.