OMAHA, Neb. (AP) — Norfolk Southern railroad is recovering from a “hardware-related technology outage” that disrupted train traffic across its network in the Eastern United States Monday, but there may be lingering effects for at least a couple of weeks.

The railroad said there is no indication that the outage was related to any cybersecurity incident. But spokesman Connor Spielmaker said Tuesday morning that “we’re continuing our investigation into the root cause of these issues.”

All system functionality was restored by 7 p.m. Eastern on Monday, the company said, and it is bringing the rail network back online.

Norfolk Southern has been in contact with its customers and is working Tuesday to get shipments where they need to be. The railroad is one of the biggest in North America with nearly 20,000 miles of track across 22 eastern states. Businesses of all kinds rely on Norfolk Southern to deliver the raw materials and goods they need while helping get their finished products to their destinations.

Norfolk Southern Corp., based in Atlanta, is in the crosshairs of federal regulators after a derailment in Ohio earlier this year led to a fiery, toxic chemical spill.

In a 143-page report this month, the Federal Railroad Administration said that Norfolk Southern has made some improvements, but is nowhere near the “gold standard for safety” its CEO is striving for. The railroad is too often only willing to meet minimum safety requirements, regulators said.

The agency has promised to conduct similar safety culture reviews at all the major freight railroads, including CSX, Union Pacific, BNSF, Canadian National and Canadian Pacific Kansas City, but it hasn’t set a timeline for those reviews.

Congress and regulators have called for all the major freight railroads to make a number of changes to improve safety but proposed legislation has stalled in the Senate and failed to get started in the Republican-controlled House.