WASHINGTON — Maine’s U.S. Reps. Mike Michaud and Chellie Pingree continued to press Wednesday for stronger safety standards for tanker rail cars during a meeting with the head of an agency that oversees the transportation of hazardous materials.

The meeting with Cynthia Quarterman — the administrator of the Department of Transportation’s Pipeline and Hazardous Materials Safety Administration — was the third meeting between the representatives and top federal transportation officials this month.

Pingree and Michaud, both Democrats, requested the meetings soon after the derailment and explosion of a crude oil train killed 47 people in Lac-Megantic, Quebec, a town not far from Maine’s border. The pair previously met with Deborah Hersman, chairman of the National Transportation Safety Board, and Joseph Szabo, administration of the Federal Railroad Administration.

According to their offices, the two representatives discussed the “frustratingly slow” process of updating safety requirements for widely used rail tank cars such as those involved in the Quebec disaster.

Quarterman’s agency has been working on the rules for more than a year and originally planned to publish its recommendations in October 2012. But the agency has pushed back that timeframe — citing the need for “additional coordination” — and is now slated to wrap up public comment on the proposals at the end of November.

Officials announced plans this week for a public review of federal regulations for transporting hazardous materials by rail, slated for Aug. 27-28 in Washington, D.C.

“The federal rulemaking process is a cumbersome one, but we need to avoid any further delays, especially given the exponential growth of hazardous material shipments,” Pingree and Michaud said in a joint statement Wednesday. “Whether it’s oil, ethanol, or some other hazardous material traveling on our nation’s tracks, the American people deserve to know that these shipments are being carried in tanker cars that are designed to the highest safety standards.”

Pingree is married to S. Donald Sussman, majority owner of MaineToday Media, which publishes the Portland Press Herald, the Kennebec Journal and the Morning Sentinel.

Safety concerns about the DOT-111 rail cars are not new. The National Transportation Safety Board first raised concerns about the DOT-111 cars in 1991. Studies have found that the cars are prone to rupture during crashes, prompting the NTSB to recommend that the Pipeline and Hazardous Materials Safety Administration release new safety and design standards for the cars.

The Montreal, Maine & Atlantic Railway train that derailed in Lac-Megantic earlier this month was hauling 72 cars — each of them DOT-111 cars — filled with crude oil from the Bakken oil fields of North Dakota. The train was en route to an Irving refinery in St. John, N.B., when the engineer parked the train outside of Lac-Megantic for the night. The unattended train’s brakes failed however, sending the train barreling down eight miles of tracks before derailing in the center of the lakeside tourist town.

The Canadian investigation is ongoing. The incident has prompted discussion of regulatory changes in Canada and the U.S. as more crude oil moves via rail.

Kevin Miller — 317-6256

kmiller@mainetoday.com.