The deadly gas line explosion in San Bruno was less than four years ago, and a new report shows the inspection of risky pipelines hasn't improved.

That was the finding of the Transportation Department's Office of Inspector General, a government watchdog.

The report says the Pipeline and Hazardous Materials Safety Administration isn't ensuring key state inspectors are properly trained, inspections are being conducted frequently enough and inspections target the most risky pipelines.

"As part of our commitment to safety, we are constantly looking to identify and fix potential vulnerabilities to ensure pipelines continue to operate safely and reliably," PHMSA spokesman Damon Hill said. 

Hill defends his agency by saying pipelines are a shared responsibility with state agencies.