HOUSTON (Reuters) - Marathon Petroleum Corp evacuated workers from a portion of its Galveston Bay refinery in Texas City, Texas on Wednesday due to a butane leak, the company said, but no injuries were reported.

A backhoe struck a butane pipeline near butane storage spheres and the 31,500 barrel per day (bpd) Alkylation 3 Unit at about 9 a.m. CDT (1400 GMT), sources familiar with plant operations said. Butane continued to be released from the pipeline until shortly 12 p.m. CDT.

The company said a butane line was damaged during maintenance.

"There were no injuries and no impact to the community or refinery," said Marathon spokesman Jamal Kheiry in an email. "As a precaution, some personnel in the area (of the leak) were evacuated."

By early afternoon, Marathon said it was monitoring the butane line for any recurrence of the leak.

Late last month, Marathon shut the 459,000 bpd refinery's two coking units and two hydrotreaters for an overhaul expected to last about a month.

Texas City Emergency Management Director Derek Duckett said city officials were notified of the butane release on Wednesday morning. "No action was needed by the city as we were not impacted by the incident," Duckett said in an email.

Highly flammable butane is cooled and stored as a liquid, but converts to gas at atmospheric temperatures.

A 2007 pipe leak triggered a butane gas cloud explosion at Valero Energy Corp's McKee refinery in Sunray, Texas, which forced an evacuation of the refinery and a three-mile area around it for fear the ensuing fire would cause one of the butane storage spheres to explode.

In 2005, while under the ownership of BP Plc, the Galveston Bay refinery was the site of the deadliest U.S. refinery accident so far this century when 15 workers were killed and 180 others injured in a hydrocarbon vapor cloud explosion.

In April 2015, former and current employees told Reuters, Marathon had rolled back policies implemented by BP following the 2005 explosion to improve safety at the refinery. Marathon purchased the refinery from BP in 2013.

(Reporting by Erwin Seba; editing by Diane Craft, G Crosse)