OMAHA, Neb. (AP) — Federal regulators have proposed suspending a Trump administration rule that would have allowed railroads to haul liquefied natural gas while they take a closer look at the potential safety risks. The rule, which was backed by both the natural gas and freight rail industries, had already been on hold because several environmental groups and 14 states filed lawsuits challenging it. In their lawsuit, environmental groups argued that those new railcars required by the rule were untested and might not withstand high-speed impacts, increasing the threat of an explosive train derailment along rail lines that cross directly through the heart of most cities.