Transport Canada is investigating whether any federal rules or regulations were broken in connection to the deadly train derailment in Lac-Mégantic, Que., in July.

CBC News has learned that Transport Canada is searching the New Brunswick offices of Irving Oil after obtaining a search warrant this week to help determine whether all safety rules were followed.

"Transport Canada is carrying out its investigation at the offices of Irving Oil in Saint John, New Brunswick," a spokesperson for Transport Minister Lisa Raitt told CBC News Friday.

The rules and regulations are set out in the Railway Safety Act and the Transportation of Dangerous Goods Act, which are administered by Transport Canada.

A spokesperson for Irving Oil confirmed the company had been contacted by Transport Canada but said "operations remain normal."

"We have received requests from government investigators regarding our operations. We continue to fully co-operate with them, complying with all requests for information," Sam Robinson told CBC News in an email.

The Opposition New Democrats have been calling on the federal government to step up rail safety, in particular the transportation of dangerous goods.

"Unfortunately, it took Lac-Mégantic for the government to realize that crude oil is dangerous goods," Hoang Mai, the NDP's deputy critic for transport, told CBC News on Friday,

"We have to look at federal regulations, it's something we've been asking for a long time."

Raitt's office also confirmed Friday that the federal government is considering new rules for the transportation of crude oil by rail.

A spokesperson for the Canadian Association of Petroleum Producers said the industry already has an emergency response plan in place.

"Those things may add cost but they also provide care and custody and assurance, so striking the right balance to make sure we are safe, we feel is important too," the spokesperson said.

In September, the independent Transportation Safety Board said its preliminary investigation had found that the rail cars may have been mislabelled and were carrying a form of crude oil that was more combustible than what was indicated on the tankers. The TSB's investigation is also ongoing.

Crude oil on a train was destined for Irving's refinery in Saint John when cars derailed and exploded in the Quebec town, killing 47 people.

With files from CBC's Susan Lunn and Karen Pauls